JP2005088071A - Composite material for brazing and brazed product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite material for brazing which has excellent brazing characteristic and excellent heat resistance and corrosion resistance in a brazed portion, and to provide a brazed product which is excellent in reliability of the brazed portions and is low in its manufacturing cost. <P>SOLUTION: This composite material 10 for brazing is used to braze members to be brazed to each other, and is composed of a brazing material 15 of a composite layer structure with a Ni layer or a Ni-alloy layer 13 and a Ti layer or a Ti alloy layer 12 overlapped each other. The ratio W1/W2 is 0.60-0.68, wherein W1 denotes the weight of Ni component contained in the brazing material 15, and W2 denotes the total weight of the Ni component and the Ti component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a brazing composite material and a brazing product using the same, and more particularly to a composite material used for brazing a heat exchanger and a fuel cell member and a brazing product using the same.

  Stainless steel-based clad materials are used as joining materials for automobile oil coolers. In this case, a Cu material having a function as a brazing material is clad on one side or both sides of a stainless steel plate as a base material.

  Further, as a brazing material for members made of stainless steel, Ni-base or Co-base alloy, various Ni brazing materials having excellent corrosion resistance at the brazed joint are defined by JIS standards.

  Further, a powder obtained by adding 4 to 22 wt% of a metal powder selected from Ni, Cr, or Ni—Cr alloy to a powdered Ni brazing material as a Ni brazing material used for joining a heat exchanger. Ni brazing filler metal has been proposed (see, for example, Patent Document 1).

  Further, there is a self-brazing composite material having a brazing layer made of Ni and Ti on the surface of stainless steel as a base material, that is, having a brazing layer structure of Ni / Ti / stainless steel (for example, Patent Document 2). reference).

JP 2000-107883 A Japanese Patent Laid-Open No. 7-299592

  By the way, a conventional brazing material or a brazing composite material is subjected to a heat exchanger (cooler for a fuel cell reformer, exhaust gas recirculation device (hereinafter referred to as EGR (Exhaust Gas)) exposed to a highly corrosive gas or liquid at high temperature. When used as a brazing filler metal for a recirculation)), there are the following problems.

  (1) When the aforementioned stainless steel-based clad material is used as a joining material for an oil cooler for automobiles, there is no problem with respect to heat resistance and corrosion resistance. However, when this stainless steel-based clad material is used as a bonding material for an EGR cooler, the exhaust gas is circulated at a high temperature and highly corrosive in the EGR cooler. (Cu material) has a problem that heat resistance and corrosion resistance are not sufficient.

  (2) Since the powder Ni brazing material described in Patent Document 1 and various Ni brazing materials specified in JIS standards are in the form of powder, the work of applying the powder Ni brazing material to each brazed joint is performed. I need it. That is, since much work is required for the brazing work, the productivity of the brazed product is remarkably lowered, resulting in an increase in manufacturing cost.

  (3) Since the amorphous Ni brazing material similarly stipulated by the JIS standard is very fragile, handling (handling) at the time of brazing material manufacture and brazing product assembly is difficult, and there has been a problem that the work cost becomes high.

  (4) Although the self-brazing composite material described in Patent Document 2 is sufficient in heat resistance and corrosion resistance, the brazing material itself is not good in brazing and wettability during brazing. Since it is brittle, there has been a problem that the performance (strength and fatigue properties) of the product after brazing is greatly reduced.

  One object of the present invention created in view of the above circumstances is to provide a brazing composite material having good brazing characteristics and good heat resistance and corrosion resistance of a brazed joint. .

  Another object of the present invention is to provide a brazed product in which the reliability of the brazed joint is good and the manufacturing cost is low.

  In order to achieve the above object, a brazing composite material according to the present invention brazes members to be brazed and has a multilayer structure in which a Ni or Ni alloy layer and a Ti or Ti alloy layer are stacked. A ratio W1 / W2 between the weight W1 of the Ni component contained in the brazing material and the total weight W2 of the Ni component and the Ti component is 0.60 to 0.68.

  Here, it is preferable that at least one of the Ni or Ni alloy layer or the Ti or Ti alloy layer contains P. Thereby, the hot water flow property when brazing the brazing material and the oxidation resistance of the brazed joint can be further improved.

  Moreover, it is preferable that at least one of Ni or Ni alloy layer or Ti or Ti alloy layer contains at least one of Cu, Mn, Al, or Cr. Thereby, the hot-water flow property when brazing the brazing material and the corrosion resistance of the brazed joint can be further improved.

  According to the above, the brazing material is formed by cladding the Ti or Ti alloy layer and the Ni or Ni alloy layer at a predetermined weight ratio, so that the brazing characteristics are good and the brazing joint A composite material for brazing having good heat resistance and corrosion resistance can be obtained.

  According to the present invention, it is possible to braze a Ni—Ti brazing material at a relatively low temperature, and exhibit an excellent effect that the reliability of the brazed joint is high.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

  The present inventors have good brazing characteristics (such as hot metal flowability and brazing productivity of the brazing material), good heat resistance and corrosion resistance of the brazed joint, and greatly reduce the brazing cost. Various studies were made on the composition of the brazing composite. As a result, conventionally, Ni metal alone has a high melting point of about 1455 ° C., and as such (single), it was difficult to use it as a brazing material for joining stainless steel materials. It was found that the melting point can be lowered by cladding at a weight ratio and alloying these at the time of brazing, and brazing at around 1200 ° C. is possible.

  A cross-sectional view of a brazing composite material according to a preferred embodiment of the present invention is shown in FIG.

  As shown in FIG. 1, a brazing composite material 10 according to the present embodiment is for brazing materials to be brazed together, and has a thin plate-like Ti or Ti alloy layer 12 and Ni or It is composed of a brazing material 15 clad with two layers of Ni alloy layer 13.

  Moreover, the composite material 10 adjusted the ratio (W1 / W2) of the weight W1 of the Ni component contained in the brazing material 15 and the total weight W2 of the Ni component and the Ti component to 0.60 to 0.68. Is. In other words, the composite material 10 is adjusted so that the composition of the entire brazing material 15 is Ni-32 to 40 wt% Ti. These adjustments are made by adjusting the layer thickness of the layers 12 and 13, adjusting the alloy composition of the layers 12 and 13, and the like. Here, if W1 / W2 is less than 0.60, the melting point of the brazing material 15 is increased, and the hot water flowability is deteriorated. On the other hand, if W1 / W2 exceeds 0.68, the melting point of the brazing material 15 is also increased, and the temperature range in which the liquid phase and the solid phase coexist is widened, and the hot water flowability is deteriorated.

  At least one of the layer 12 or the layer 13 may contain P. By containing 0.02 to 10 wt%, preferably 0.02 to 5.0 wt% of P in the brazing material 15, the hot metal flow and oxidation resistance of the brazing material can be remarkably improved. Here, the reason why the P content is limited to 0.02 to 10 wt% is that if it is less than 0.02 wt%, improvement in hot water flow cannot be expected, and conversely if it exceeds 10 wt%, brazing is performed. This is because the strength is lowered depending on the type of brazed member to be used.

  Moreover, at least one of the layer 12 or the layer 13 may contain at least one of Cu, Mn, Al, or Cr. By containing Cu and / or Mn in the brazing material 15, the hot water flow property of the brazing material 15 can be further improved. Here, the Cu concentration contained in the brazing material 15 is 0.2 to 30 wt%. This is because if the Cu concentration is less than 0.2 wt%, the effect of Cu addition cannot be obtained sufficiently, and conversely if it exceeds 30 wt%, the corrosion resistance decreases. On the other hand, the inclusion of Al and / or Cr in the brazing material 15 can further improve the corrosion resistance and high-temperature oxidation resistance of the brazed joint.

  A composite material for brazing (final product) having a desired thickness is obtained by appropriately rolling the composite material 10 according to the present embodiment. The final product is placed between a pair of brazed members (not shown) to be joined, and subjected to a brazing process by heating, whereby a brazed product is obtained. Brazing products include heat exchangers exposed to high-temperature, highly corrosive gases or liquids such as EGR coolers, fuel cell reformer coolers, fuel cell members, oil coolers, radiators, secondary battery members, etc. Can be mentioned.

  In the present embodiment, the description has been made using the composite material 10 having a thin plate shape, but the shape of the composite material is not particularly limited to the thin plate shape, and a modification of FIG. 1 is shown in FIG. Further, the Ni or Ni alloy layer 13 may be formed on the surface of the rod-like or wire-like Ti or Ti alloy 22 to form the brazing composite material 20. In this case, the Ni or Ni alloy layer 13 is formed by a plating method, an extrusion method, a pipe making method, or the like.

  Next, the operation of the composite material 10 (or 20) according to the present embodiment will be described.

  In the composite material 10 (or 20) according to the present embodiment, the brazing material 15 is composed of the Ti or Ti alloy layer 12 (or Ti or Ti alloy 22) and the Ni or Ni alloy layer 13. . For this reason, during brazing, the Ni component of the Ni brazing material is mixed (melted) into the Ti brazing material. As a result, the melting point of the brazing material containing Ni or Ni alloy, which has been difficult to function as a brazing material because of its high melting point, can be lowered, and brazing using the composite material 10 can be performed at around 1200 ° C. It becomes possible. As a result, the composite material 10 (or 20) according to the present embodiment can be used as a brazing material for joining an EGR cooler that is exposed to a highly corrosive gas or liquid at a high temperature. As a result, it is possible to obtain a Ni—Ti brazed joint having excellent brazing characteristics and excellent heat resistance and corrosion resistance.

  In addition, the surface of the brazed joint can be obtained by containing Al or Cr in at least one of the Ti or Ti alloy layer 12 (or Ti or Ti alloy 22) and the Ni or Ni alloy layer 13 of the brazing material 15. Further, a dense oxide film made of aluminum oxide or chromium oxide is formed, and the high temperature oxidation resistance can be remarkably improved. As a result, it becomes difficult for the joint strength of the brazed joint to decrease due to high-temperature (about 600 to 800 ° C.) oxidation, and the joint of the brazed product has good reliability.

  Further, by adding Cu or Mn to at least one of the Ti or Ti alloy layer 12 (or Ti or Ti alloy 22) and the Ni or Ni alloy layer 13 of the brazing material 15, the viscosity of the brazing material 15 is increased. Decreases. As a result, the flowability of the brazing material 15 is further improved, and the brazing characteristics are improved.

  As described above, brazing joints having excellent heat resistance and corrosion resistance can be obtained by brazing using the composite material 10 (or 20) according to the present embodiment, and the gas is highly corrosive at high temperatures. Alternatively, it is optimal as a brazing material for brazed joints such as EGR coolers exposed to liquid.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 3 shows a cross-sectional view of a brazing composite material according to another preferred embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and detailed description is abbreviate | omitted about these members.

  The composite material 10 according to the previous embodiment is composed of a brazing material 15 in which a thin plate-like Ti or Ti alloy layer 12 and a Ni or Ni alloy layer 13 are stacked in two layers.

  On the other hand, as shown in FIG. 3, the composite material 30 according to the present embodiment includes a thin plate-like Ti or Ti alloy layer 12 and Ni or Ni alloy layers 33 a and 33 b, and a layer 33 a and a layer 12. The brazing material 35 is alternately stacked in three layers with the layer 33b.

  Also in the composite material 30 according to the present embodiment, the same effects as those of the composite material 10 according to the previous embodiment can be obtained.

  In the present embodiment, the brazing material 35 having a three-layer structure has been described. However, the present invention is not limited to this, and as shown in FIG. Alternatively, the brazing material 45 may be formed by alternately stacking the Ti alloy layers 12 and 12 and the Ni or Ni alloy layers 43 a to 43 c on the five layers alternately with the layers 43 a, 12, 43 b, 12, and 43 c. Further, a brazing material having a four-layer structure or a structure having six or more layers may be used.

  Further, in the present embodiment, the description has been made using the composite material 30 having a thin plate shape, but the shape of the composite material is not particularly limited to the thin plate shape, and FIG. As shown in FIG. 5, a brazing layer 55 is formed on the surface of a rod-like or wire-like Ni or Ni alloy 53a, the inner layer side being a Ti or Ti alloy layer 12, and the outer layer side being a Ni or Ni alloy layer 53b. The composite material 50 may be used. Further, as shown in FIG. 6, a third modification of FIG. 3 is laminated on the surface of a rod-like or wire-like Ni or Ni alloy 63a with layers 12, 63b, 12 and 63c in order from the inner layer side. The brazing layer 65 to be formed may be formed as the brazing composite material 60.

  In this embodiment, the case where the materials (composition) of the layers 33a and 33b are the same has been described. However, the present invention is not limited to this, and the material (composition) may be different for each layer.

  As mentioned above, it cannot be overemphasized that embodiment of this invention is not limited to embodiment mentioned above, and various things are assumed in addition.

  Next, embodiments of the present invention will be described based on examples, but the embodiments of the present invention are not limited to these examples.

(Example 1)
A Ni strip with a thickness of 0.45 mm, a Ti strip with a thickness of 1.0 mm, and a Ni strip with a thickness of 0.45 mm are clad by a rolling method, and the laminated structure is Ni / Ti / Ni, the entire brazing material A composite material having a composition of Ni-36Ti (wt%; W1 / W2 = 0.64) was produced. Thereafter, the composite material was repeatedly rolled to produce a brazing composite material having a total brazing material thickness of 70 μm. This composite material is placed on a SUS304 (JIS standard) strip having a thickness of 0.6 mm to form a structure of Ni / Ti / Ni / SUS and heated in a tubular furnace at 1200 ° C. for brazing. The properties of the composite materials were evaluated.

(Example 2)
For brazing, in the same manner as in Example 1, except that the thickness of each Ni strip is 0.38 mm and the composition of the entire brazing material is Ni-40Ti (wt%; W1 / W2 = 0.60). The properties of the composite were evaluated.

(Comparative Example 1)
Rolling was repeatedly performed on a Ni strip having a thickness of 0.5 mm, and the brazing material was entirely made of Ni and a brazing material having a thickness of 70 μm was produced. This brazing material is placed on a SUS304 (JIS standard) strip with a thickness of 0.6 mm to form a structure of Ni / SUS, and heated in a tubular furnace at 1200 ° C., and the characteristics of the brazing material Evaluated.

(Comparative Example 2)
For brazing, in the same manner as in Example 1, except that the thickness of each Ni strip was 0.59 mm and the composition of the entire brazing material was Ni-30Ti (wt%; W1 / W2 = 0.70). The properties of the composite were evaluated.

(Comparative Example 3)
For brazing, in the same manner as in Example 1, except that the thickness of each Ni strip was 0.35 mm and the composition of the entire brazing material was Ni-42Ti (wt%; W1 / W2 = 0.58). The properties of the composite were evaluated.

(Comparative Example 4)
For brazing, as in Example 1, except that the thickness of each Ni strip is 0.32 mm and the composition of the entire brazing material is Ni-44Ti (wt%; W1 / W2 = 0.56). The properties of the composite were evaluated.

(Conventional example 1)
A composite material made of SUS304 (JIS standard), clad with a copper strip on the surface of a stainless steel strip with a thickness of 2.5 mm by a rolling method, a laminated structure of Cu / SUS, and the entire brazing layer made of Cu. Produced. Thereafter, the composite material was repeatedly rolled to produce a brazing composite material having a total brazing layer thickness of 70 μm (0.07 mm). This composite material was heated in a tubular furnace at 1120 ° C. to evaluate the characteristics of the brazing composite material.

(Conventional example 2)
A composite material for brazing was applied to the surface of the same stainless steel strip as in Comparative Example 1 by applying a kneaded material prepared by dissolving a commercially available powdered Ni brazing material (composition: Ni-19Cr-10Si (wt%)) with a synthetic resin binder. Was made. Thereafter, the characteristics of the brazing composite material were evaluated in the same manner as in Comparative Example 1. The brazing temperature was 1180 ° C.

  About each composite material and brazing material of Examples 1 and 2, Comparative Examples 1 to 4, and Conventional Examples 1 and 2, evaluation of characteristics, specifically, fillet formation state (hot water flowability), presence or absence of corrosion occurrence (Corrosion resistance), brazing productivity evaluation (workability), and comprehensive evaluation of these characteristics. The evaluation results of the brazing characteristics are shown in Table 1. The evaluation was evaluated as 極 め て for very good, ◯ for good, △ for insufficient (insufficient), and × for poor.

  Here, the evaluation of the molten metal flowability is performed by placing a stainless steel pipe made of SUS304 on the surface of the brazing material or brazing layer of each composite material, and brazing the brazed portion when heated to 1200 ° C. Evaluation was performed by the shape and the cross-sectional area of the fillet.

  Corrosion resistance is evaluated by immersing each composite material after brazing in a corrosive solution containing chlorine ions, nitrate ions and sulfate ions for 1000 hours, and then performing a corrosion test. This was done by examining the structure of the brazed part and examining the occurrence of corrosion. In addition, the solution after the corrosion test was analyzed, and the amount of the eluate from the brazing material was quantitatively compared to determine the degree of corrosion.

  As shown in Table 1, in the composite materials of Examples 1 and 2 which are the composite materials for brazing according to the present invention, the brazing material is a clad layer of a Ti layer and a Ni layer, and the composition of the brazing material Was adjusted to Ni-32 to 40 wt% Ti (W1 / W2 = 0.60 to 0.68), so the melting point of Ni could be lowered during brazing, and brazing at about 1200 ° C. was possible. . As a result, the composite materials of Examples 1 and 2 had extremely good hot water flowability. In addition, the composite materials of Examples 1 and 2 had no corrosion, good brazing productivity, and overall evaluation was extremely good.

  In contrast, the brazing material of Comparative Example 1 had good brazing productivity, but the brazing material was composed of Ni alone, so that the brazing material was at a brazing temperature of 1200 ° C. It did not melt and did not function as a brazing material. From the above, the overall evaluation was poor.

  The composite material of Comparative Example 2 had no corrosion and good brazing productivity, but the Ni content in the brazing material was too high (Ni-30wt% Ti (W1 / W2 = 0.70)). Therefore, the melting point of the brazing material was high. For this reason, the hot water flowability was not good (bad), and as a result, the overall evaluation was bad.

  The composite material of Comparative Example 3 had no corrosion and good brazing productivity, but the Ni content in the brazing material was too small (Ni-42 wt% Ti (W1 / W2 = 0.58)). Therefore, although the melting point itself of the brazing material is relatively low, the temperature range in which the solid phase and the liquid phase coexist is wide. Therefore, the flowability of the brazing water is not sufficient (insufficient), and as a result, the overall evaluation is insufficient.

  The composite material of Comparative Example 4 had no corrosion and good brazing productivity, but the Ni content in the brazing material was even smaller than that of Comparative Example 3 (Ni-44 wt% Ti (W1 Therefore, the melting point of the brazing material was high and the temperature range where the solid phase and the liquid phase coexisted was wide. Therefore, the flowability of the brazing water was not good (bad), and as a result, the overall evaluation was bad.

  Although the composite material of Conventional Example 1 had very good hot metal flow and brazing productivity, the brazing layer was composed of Cu alone, so that the corrosion resistance was not good and corrosion occurred. As a result, the overall evaluation was poor.

  The composite material of Conventional Example 2 has extremely good hot-water flow properties, and no corrosion occurred. However, since the brazing material of the brazing layer is a powder Ni brazing material, a binder is required to form the brazing layer. The brazing productivity was bad. As a result, the overall evaluation was poor.

  As mentioned above, since the composite material of Examples 1 and 2 which is a composite material for brazing according to the present invention is good in brazing metal flowability, corrosion resistance of the brazed joint, and brazing productivity, It can be seen that the composite material for brazing is excellent in brazing characteristics and reliability of the brazed joint.

  The composite material according to a preferred embodiment of the present invention is not limited to a heat exchanger that is exposed to a highly corrosive gas or liquid at a high temperature such as an EGR cooler. For example, the present invention can be applied to various uses such as a fuel cell reformer cooler and a fuel cell member. In particular, a rod-like or wire-like composite material (see FIGS. 2, 5, and 6) has a small diameter size and good handleability, so that it can be used for EGR coolers, fuel cell reformer coolers, and the like. In addition to heat exchangers and fuel cell members, the present invention can also be applied to oil coolers, radiators, secondary battery members, and the like.

1 is a cross-sectional view of a brazing composite material according to a preferred embodiment of the present invention. It is sectional drawing which shows the modification of FIG. It is sectional drawing of the composite material for brazing which concerns on other preferable one Embodiment of this invention. It is sectional drawing which shows the 1st modification of FIG. It is sectional drawing which shows the 2nd modification of FIG. It is sectional drawing which shows the 3rd modification of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Composite material for brazing 12 Ti or Ti alloy layer 13 Ni or Ni alloy layer 15 Brazing material

Claims (6)

  In a brazing composite material for brazing members to be brazed, it is composed of a brazing material having a multilayer structure in which a Ni or Ni alloy layer and a Ti or Ti alloy layer are stacked, and Ni contained in the brazing material A brazing composite material having a ratio W1 / W2 of the weight W1 of the component and the total weight W2 of the Ni component and the Ti component is 0.60 to 0.68.   The brazing composite material according to claim 1, wherein at least one of the Ni or Ni alloy layer or the Ti or Ti alloy layer contains P.   The composite material for brazing according to claim 1 or 2, wherein the P concentration contained in the brazing material is 0.02 to 10 wt%.   The brazing composite material according to any one of claims 1 to 3, wherein at least one of the Ni or Ni alloy layer or the Ti or Ti alloy layer contains at least one of Cu, Mn, Al, and Cr.   The brazing composite material according to any one of claims 1 to 4, wherein a concentration of Cu contained in the brazing material is 0.2 to 30 wt%. A brazed product using the brazing composite material, wherein the brazing composite material is joined using the brazing composite material according to any one of claims 1 to 5.

Images