JP4893542B2 - Brazing composite material and brazing product using the same - Google Patents

Description

  The present invention relates to a brazing composite material (a composite material for brazing processing) and a brazing product using the same, and in particular a brazing composite material capable of improving brazing performance and heat resistance and corrosion resistance. The present invention relates to a brazing product using this.

  As a brazing composite material composed of a brazing layer in which a plurality of metal layers are laminated, for example, a stainless-based clad brazing material is used as a joining material for an oil cooler for automobiles. In this case, Cu having a function as a brazing material is clad on one side or both sides of a stainless steel plate.

  In addition, as a brazing material for parts such as stainless steel and Ni-based and Co-based alloys, various Ni brazing materials excellent in oxidation resistance and corrosion resistance of joints are defined by JIS standards.

  Furthermore, as described in Patent Document 1 as a Ni brazing material for joining heat exchangers, 4 to 22% by weight of a metal powder selected from Ni, Cr and Ni—Cr alloy is added to a powdered Ni brazing filler metal. A Ni brazing material constituted as described above has been proposed.

  Moreover, as a method for producing a self-brazing composite material, there is a method for producing a composite material as described in Patent Document 2.

JP 2000-107883 A Japanese Patent Laid-Open No. 7-299592 JP 2002-363707 A

  However, the composite material obtained by the manufacturing method described in Patent Document 2 has the following problems at the time of brazing.

  The brazing material in the brazing composite material of the prior art is an alloy oxidation centered on the Ti component on the brazing portion surface when the brazed portion after brazing is exposed to a high temperature atmosphere containing oxygen of 600 ° C. or more for a long time. Things are formed. Since the alloy layer constituting the brazing portion is mainly composed of Ti, it easily reacts with oxygen, oxygen diffuses remarkably from the surface toward the inside, and the brazing portion undergoes significant oxidation from the surface. Oxidation proceeds with time, and the oxide layer formed on the surface of the brazed portion becomes thicker.

  Since the oxide layer formed in this way has a brittle nature, if the brazing part is oxidized significantly, the joining strength of the brazing part will be significantly reduced, and the overall strength of the brazing composite material will be significantly reduced. There is a problem.

  Accordingly, an object of the present invention is to provide a brazing composite material that suppresses the progress of oxidation in a brazing portion when exposed to a high-temperature oxidizing atmosphere for a long time after brazing, and a brazed product using the same.

The present invention was devised to achieve the above object, and the invention of claim 1 is characterized in that a brazing layer in which a plurality of metal layers are laminated is formed on the surface of a base material made of stainless steel , wax layer, in order from the substrate side, a layer consisting of Ni -Nb alloy containing Nb 0.5 to 1.0 wt%, a pure Ti or Al 6% by weight, Ti-Al- containing V 4 wt% Each metal layer is composed of a layer made of a V alloy, an Invar alloy containing 36% by weight of pure Fe or Ni, or a layer made of a stainless steel of SUS304 , and Nb is 0.2 to 1. This is a brazing composite material containing 5% by weight.

The invention of claim 2 is a brazed product assembled by using the brazing composite material of claim 1 .

  According to the present invention, the high temperature oxidation resistance in the brazed portion after brazing is improved.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a brazing composite material showing a preferred embodiment of the present invention.

  As shown in FIG. 1, a brazing composite material 1 according to this embodiment is mainly used for a heat exchanger (such as an exhaust gas recirculation (EGR) cooler or a fuel cell reformer cooler) or a fuel cell. Used as a member.

  For example, when the brazing composite material 1 is used in a heat exchanger, a base material such as stainless steel after rolling becomes a plate that defines a flow path of the heat exchanger, and a member that joins the plates to each other is a brazing layer. Become.

  That is, after processing the brazing composite material 1 into an appropriate shape, the brazing composite material 1 is superposed to form a heat exchanger assembly, which is heated in a heating furnace (for example, around 1200 ° C.). Heat and hold to 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, the brazing composite material 1 is described as an example in which a plate-like base material such as a plate used in a heat exchanger and a brazing layer are combined, but the brazing composite material 1 according to the present embodiment. As the above, it includes those composed only of the brazing layer before being bonded to the base material.

  The brazing composite material 1 is obtained by forming a brazing layer (brazing material) 3 formed by laminating a plurality of metal layers on the surface of a base material (base material) 2. Each metal layer of the brazing layer 3 is composed of three layers of a Ti or Ti alloy layer 4, a Ni or Ni alloy layer 5, and a Fe or Fe alloy layer 6 that are sequentially laminated from the base material 2 side.

  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 may be used as the Fe-based alloy. In addition to SUS304, most stainless steels such as SUS310, SUS316, and SUS430 can be used.

  As the Ni alloy, in addition to the Ni—Nb alloy, a Ni—P alloy, a Ni—Cr—Fe alloy, or the like may be used. However, also in that case, it is a premise that the Nb component contained in the Ni alloy is 0.3 to 3.0% by weight as described later.

  Ti-6Al-4V, Ti-4Al-4V, etc. can be used as the Ti alloy. As the Fe alloy, stainless steel such as Fe-Ni alloy (Fe-36Ni alloy (Invar), etc.), austenite (Fe-Cr alloy, etc.), ferrite (Fe-Cr-Ni alloy, etc.) is used. Good.

  Now, in the brazing composite material 1 according to this embodiment, Nb is 0.2 to 1.5% by weight (mass%) with respect to the entire brazing layer 3 (in the components of the entire brazing layer 3), preferably Is contained in an amount of 0.2 to 1.0% by weight, more preferably 0.25 to 0.7% by weight.

  This is because if Nb is less than 0.2% by weight, the content is too small and sufficient high-temperature oxidation resistance cannot be obtained, and if it exceeds 1.5% by weight, the melting point of the brazing layer will increase. This is because the brazing temperature must be high, and problems arise in brazing and heat treatment costs.

  More specifically, Ni or Ni constituting the brazing layer 3 in order to contain 0.2 to 1.5% by weight of Nb with respect to the entire brazing layer 3 (Nb is preliminarily contained in the brazing layer 3). The alloy layer 5 may contain 0.3 to 1.5% by weight of Nb.

  In addition, as a method of previously containing Nb in the brazing layer, for example, there is a method of using a Ni alloy layer 5 constituting the brazing layer 3 made of a Ni alloy containing Nb. This is because Nb is alloyed with Ni relatively easily. When using a Ni alloy containing Nb, the Nb component contained in the Ni alloy is preferably 0.3 to 3.0% by weight.

  If the amount is less than 0.3% by weight, the amount is too small to exhibit the effect of the invention. If the amount exceeds 3.0% by weight, the mechanical strength of the Ni alloy increases too much, and the brazing of the brazing layer is performed. This is because it becomes difficult.

  The operation of this embodiment will be described.

  When the brazing composite material 1 is used for a heat exchanger, the brazing composite materials 1 (or the brazing composite material 1 and other members) are heated and melted to form a brazing composite material 1. The parts in contact with each other (the brazing layer 3) are heated and melted and brazed. That is, in the brazing composite material 1, the Ti or Ti alloy layer 4, the Ni or Ni alloy layer 5, the Fe or alloy layer 6 is clad on the base material 2, and this is rolled to form the brazing layer 3.

For example, the brazing composite material 1 is used to braze with stainless steel. The heat treatment atmosphere is performed in a vacuum of 7 × 10 ⁻² Pa or less (not a high vacuum). 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, so that the brazing composite material 1 is brazed to each other. An attachment material is obtained.

  Furthermore, if this brazing material is processed into a predetermined shape and assembled, for example, heat exchangers (exhaust gas recirculation (EGR) coolers, fuel cell reformer coolers, etc.), fuel cell members, etc. A brazed product is obtained.

  During the brazing described above, the metal layer constituting the brazing layer 3 and a part of the substrate 2 are melted to form an alloy of the brazing portion. At this time, in the brazing composite material 1, since Nb is included in an amount of 0.2 to 1.5 wt% with respect to the entire brazing layer 3, carbon components inevitably contained in the respective metal layers and the base material 2, The carbon component supplied from the brazing atmosphere reacts with the Ti component and the Nb component in the brazing part, even though they are in a small amount, and is dispersed as Ti carbide and Nb carbide in the brazing part alloy, respectively. To do. This is because Ti and Nb easily react with carbon among metal elements.

  In this way, when the brazed brazing material is exposed to an atmosphere containing oxygen (for example, in the air) at a high temperature of 600 ° C. or higher, the oxygen component in the atmosphere diffuses from the brazing portion surface, and brazing is performed. The partial alloy is oxidized to form an oxide layer.

  However, the composite material 1 for brazing is not particularly limited in the alloy, such as on the crystal grain boundaries of the brazing alloy where the chemically stable Nb carbide formed above becomes an intrusion path of oxygen. By being dispersed in various places, it functions to prevent oxygen from penetrating into the brazing part alloy and to suppress diffusion of oxygen into the brazing part alloy.

  Thereby, in the brazing composite material 1, the diffusion rate of oxygen into the brazing part alloy is reduced, and the brazing part alloy surface of the brazing part alloy surface is less than the case where Nb is not included as in the conventional brazing composite material. Oxidation is significantly reduced.

  Therefore, according to the brazing composite material 1, the addition of Nb to the brazing layer 3 can suppress the progress of oxidation in the brazing portion when exposed to a high temperature oxidizing atmosphere for a long time after brazing. It is possible to improve the high temperature oxidation resistance in the brazed portion and to reduce the strength reduction of the entire brazing material.

  In addition, oxygen components inevitably contained in the metal layers of the brazing layer 3 and the base material 2 and oxygen components supplied from the brazing atmosphere react with the Nb component in the brazing portion, even if only a small amount. As Nb oxide, it is dispersed inside the brazing part alloy. Nb oxide, like Nb carbide, works to suppress diffusion of oxygen from the surface of the brazed part into the interior, and can suppress surface oxidation of the brazed part.

  Furthermore, the brazing composite material 1 focuses on the addition of Nb in order to increase the high temperature oxidation resistance. Nb is one of the elements added to improve corrosion resistance and oxidation resistance in stainless steel and the like, and the present inventors thought that it could be applied to a brazing composite material. Is completed.

  However, few alloys contain a certain amount or more of Nb, and some stainless steels are generally contained, but the amount is extremely small. An alloy of Ti and Nb is also partially applied to superconducting materials, but has a difficult composition. The brazing composite material 1 according to this embodiment containing 0.2 to 1.5% by weight of Nb with respect to the entire brazing layer is currently not found in the market as a general-purpose alloy.

  In addition, in the field of stainless steel, generally, by adding a small amount of Nb or Ti, Nb carbide or Ti carbide is formed at the grain boundary, and has the function of suppressing the entry of oxygen atoms from the outside. It is known to contribute to the improvement of high temperature oxidation.

  In the present invention, the above mechanism is applied to a brazing material. Certainly, the amount of carbon contained in the metal layer itself constituting the base material and the brazing material is very small in terms of specifications, but as described above, Ti constituting the brazing material easily forms a compound with carbon. As a result of experiments conducted by the present inventors, it has been found that there is a portion where Ti carbide is accumulated near the surface of the brazing portion.

  In the present invention, by further adding Nb, more carbon and oxygen are formed as Nb carbide and Nb oxide on the grain boundary of the brazing part alloy, and in the same manner as stainless steel, high temperature oxidation resistance function Improved.

  In the above 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 on both surfaces of the base material 2 and integrated.

  Also, a brazing layer having a three-layer structure of a Ti or Ti alloy layer, a Ni or Ni alloy layer, and a Fe or Fe alloy layer in order on the outer periphery of a rod-like (a core material is a base material) or wire-like base material May be combined and integrated by plating or pipe making. 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 Nb-containing Ni alloy (Ni-0.6 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 5.0 mm, coiled invar alloy with a plate thickness of 2.5 mm (Fe-36) (Weight% Ni) plates were superposed to form a total of three layers, and hot rolled to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is formed by cold rolling. To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 2)
Coiled Nb-containing Ni alloy (Ni-1.0 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 5.0 mm, coiled invar alloy (Fe-36 with a plate thickness of 2.5 mm) (Weight% Ni) plates were superposed to form a total of three layers, and hot rolled to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is formed by cold rolling. To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 3)
Coiled Nb-containing Ni alloy (Ni-0.8 wt% Nb) plate with a plate thickness of 3.4 mm, Coiled pure Ti plate with a plate thickness of 4.3 mm, Coiled stainless alloy (SUS304) plate with a plate thickness of 2.0 mm And a total of three layers were formed, and hot rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is formed by cold rolling. To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

Example 4
Coiled Nb-containing Ni alloy (Ni-0.5 wt% Nb) plate with a plate thickness of 3.4 mm, a coiled pure Ti plate with a plate thickness of 4.3 mm, and a coiled stainless alloy (SUS304) plate with a plate thickness of 2.0 mm And a total of three layers were formed, and hot rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is formed by cold rolling. To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 5)
Coiled Nb-containing Ni alloy (Ni-0.6 wt% Nb) plate with a plate thickness of 3.8 mm, a coil-like pure Ti plate with a plate thickness of 5.0 mm, and a coil-like Fe plate with a plate thickness of 1.5 mm are stacked. A total of three layers were formed, and hot rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is made by cold rolling To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 6)
Coiled Nb-containing Ni alloy (Ni-0.6 wt% Nb) plate with a plate thickness of 3.4 mm, Coiled pure Ti alloy (Ti-6 wt% Al-4 wt% V) plate with a plate thickness of 5.5 mm, A coiled invar alloy (Fe-36% by weight) with a thickness of 2.5 mm was superposed to form a total of three layers, and hot rolled to obtain a clad plate with a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) to be the base material 2 are arranged so that the Ni alloy surface of the clad material and the base material 2 are in contact with each other, and the clad material is formed by cold rolling. To do. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Comparative Example 1)
Coiled Nb-containing Ni alloy (Ni-0.1 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 5.0 mm, coiled invar alloy with a plate thickness of 2.5 mm (Fe-36) Weight% Ni) was superposed to form a total of three layers, and hot rolled to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Ni alloy surface of the clad material and the substrate are in contact with each other, and clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 2)
Coiled Nb-containing Ni alloy (Ni-3.5 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 5.0 mm, coiled invar alloy with a plate thickness of 2.5 mm (Fe-36) Weight% Ni) was superposed to form a total of three layers, and hot rolled to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Ni alloy surface of the clad material and the substrate are in contact with each other, and clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 3)
Coiled Nb-containing Ni alloy (Ni-0.1 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 4.3 mm, coiled stainless alloy (SUS304) plate with a plate thickness of 2.0 mm And a total of three layers were formed, and hot rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Ni alloy surface of the clad material and the substrate are in contact with each other, and clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 4)
Coiled Nb-containing Ni alloy (Ni-3.2 wt% Nb) plate with a plate thickness of 3.4 mm, coiled pure Ti plate with a plate thickness of 4.3 mm, coiled stainless alloy (SUS304) plate with a plate thickness of 2.0 mm And a total of three layers were formed, and hot rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Ni alloy surface of the clad material and the substrate are in contact with each other, and clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Conventional example)
A coiled Ni plate with a thickness of 3.4mm, a coiled pure Ti plate with a thickness of 8.2mm, and a coiled stainless steel alloy (SUS304) plate with a thickness of 3.4mm are stacked to form a total of three layers. Rolling was performed to obtain a clad plate having a thickness of 1.4 mm. Subsequently, a clad plate having a plate thickness of 1.0 mm was finished by cold rolling. Thereafter, the clad material and SUS304 (Cu component 0%, thickness 2.5 mm) were clad and cold-rolled by a rolling method to produce a composite substrate having a thickness of 0.5 mm.

Each of the clad materials produced in Examples 1 to 6, Comparative Examples 1 to 4 and the conventional example are cut out to 20 mm × 25 mm, and a stainless steel pipe (SUS304, φ6 mm × 15 mm) is fixed to the center with a wire or the like. A heat treatment was performed. The brazing conditions were a brazing temperature of 1150 ° C. × 15 min and a degree of vacuum of 8.0 × 10 ⁻² Pa.

  The brazing materials of Examples 1 to 6, Comparative Examples 1 to 4, and the conventional example produced under the above conditions were placed in an electric furnace maintained at 800 ° C. (atmosphere was air), and maintained for 24 hours. The brazing material was taken out. About each taken out brazing material, the oxide layer formation condition of the fillet surface of the pipe joint part in a center cross section was investigated.

  Table 1 shows the composition of each brazing composite material 1, the comparative example and the conventional brazing material, the Nb content ratio in the brazing material, and the thickness of the oxide layer on the fillet surface.

  According to Table 1, in Examples 1 to 6, compared with Comparative Examples 1 to 4 and the conventional example, the thickness of the oxide layer on the fillet surface is about 45% at the maximum and about 75% at the minimum. Therefore, it turns out that Examples 1-6 are excellent in high temperature oxidation resistance compared with a prior art example and Comparative Examples 1-4.

It is sectional drawing of the composite material for brazing which shows suitable embodiment of this invention.

Explanation of symbols

1 Brazing composite material 2 Base material 3 Brazing layer 4 Ti or Ti alloy layer 5 Ni or Ni alloy layer 6 Fe or Fe alloy layer

Claims (2)

A brazing layer in which a plurality of metal layers are laminated is formed on the surface of a base material made of stainless steel, and the brazing layer is Ni containing 0.5 to 1.0 wt% Nb in order from the base material side. A layer made of -Nb alloy , a layer made of Ti-Al-V alloy containing 6% by weight of pure Ti or Al and 4% by weight of V, an Invar alloy containing 36% by weight of pure Fe or Ni, or a stainless steel alloy of SUS304 A brazing composite material comprising a plurality of metal layers stacked and 0.2 to 1.5% by weight of Nb in the entire brazing layer. A brazed product assembled using the brazing composite material according to claim 1 .

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