Heat exchanger and method of manufacturing heat exchanger

Abstract

Mg and Bi are contained in each of a first fillet in a first braze joining portion in which a tube and a fin join, a second fillet in a second braze joining portion in which the tube and a header plate join, and a third fillet in a third braze joining portion in which the header plate and a tank body join. A concentration of Mg of each of the first to third fillets is from 0.2% or more to 2.0% or less by mass. When the tube includes a brazing material layer, a concentration of Mg of the tube at its plate thickness center is from 0.1% or more to 1.0% or less by mass. When the fin includes a brazing material layer, a concentration of Mg of the fin at its plate thickness center is from 0.2% or more to 1.0% or less by mass.

What is claimed is: 
     
         1 . An aluminum alloy heat exchanger produced by excluding flux, the heat exchanger comprising:
 a flow channel forming member to form a flow channel which a fluid flows through;   a heat transfer member having a heat transfer surface, the heat transfer member joined to a flow channel forming surface of the flow channel forming member, the heat transfer surface wider than the flow channel forming surface;   a tank member joined to the flow channel forming member to form a tank space communicating with the flow channel of the flow channel forming member;   a joining member joined to the tank member;   a first fillet formed in a first braze joining portion, in which the heat transfer member and the flow channel forming member join with each other;   a second fillet formed in a second braze joining portion, in which the flow channel forming member and the tank member join with each other; and   a third fillet formed in a third braze joining portion in which the tank member and the joining member join with each other,   wherein the flow channel forming member, the heat transfer member, the tank member and the joining member are composed of aluminum alloys, respectively,   wherein an average plate thickness of the flow channel forming member is from 0.100 mm or more to 0.400 mm or less, an average plate thickness of the heat transfer member is from 0.025 mm or more to 0.150 mm or less, an average plate thickness of the tank member is from 0.500 mm or more to 2.000 mm or less, and an average plate thickness of the joining member is from 0.500 mm or more to 2.000 mm or less,   wherein each of the first to third fillets is composed of an aluminum alloy containing magnesium, bismuth, and silicon,   wherein a concentration of the magnesium of each of the fillets is from 0.2% or more to 2.0% or less by mass,   wherein at least one of the flow channel forming member and the heat transfer member includes a brazing material layer on a surface thereof,   wherein when the flow channel forming member includes the brazing material layer, a concentration of the magnesium of the flow channel forming member at its plate thickness center is from 0.1% or more to 1.0% or less by mass, and when the heat transfer member includes the brazing material layer, a concentration of the magnesium of the heat transfer member at its plate thickness center is from 0.2% or more to 1.0% or less by mass.   
     
     
         2 . An aluminum alloy heat exchanger produced by excluding flux, the heat exchanger comprising:
 a flow channel forming member to form a flow channel in which a fluid flows through;   a heat transfer member having a heat transfer surface, the heat transfer member joined to a flow channel forming surface of the flow channel forming member, the heat transfer surface wider than the flow channel forming surface;   a reinforcing member joined to the flow channel forming member to reinforce the flow channel forming member;   a joining member joined to the reinforcing member;   a first fillet formed in a first braze joining portion in which the heat transfer member and the flow channel forming member join with each other;   a second fillet formed in a second braze joining portion in which the flow channel forming member and the tank member join with each other; and   a third fillet formed in a third braze joining portion in which the reinforcing member and the joining member join with each other,   wherein the flow channel forming member, the heat transfer member, the reinforcing member and the joining member are composed of aluminum alloys, respectively,   wherein an average plate thickness of the flow channel forming member is from 0.200 mm or more to 0.600 mm or less, an average plate thickness of the heat transfer member is from 0.025 mm or more to 0.150 mm or less, an average plate thickness of the reinforcing member is from 0.600 mm or more to 2.000 mm or less, and an average plate thickness of the joining member is from 0.600 mm or more to 2.000 mm or less,   wherein each of the first to third fillets is composed of an aluminum alloy containing magnesium, bismuth, and silicon, a concentration of the magnesium of each of the first to third fillets ranging from 0.2% or more to 2.0% or less by mass,   wherein at least one of the flow channel forming member and the heat transfer member includes a brazing material layer on a surface thereof,   wherein when the flow channel forming member includes the brazing material layer, a concentration of the magnesium of the flow channel forming member at its plate thickness center is from 0.1% or more to 1.0% or less by mass, and when the heat transfer member includes the brazing material layer, a concentration of the magnesium of the heat transfer member at its plate thickness center is from 0.2% or more to 1.0% or less by mass.   
     
     
         3 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein a concentration of the magnesium of each of the fillets is 0.3% or more by mass. 
     
     
         4 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein the flow channel forming member includes:
 a core material layer;   a brazing material layer located on one side of the core material layer; and   a cladding layer located on an opposite side to the one side of the core material layer, the cladding layer excluding brazing material,   wherein a part of the brazing material layer of the flow channel forming member is joined to a part of the cladding layer of the flow channel forming member,   wherein a concentration of the magnesium in a surface layer of the cladding layer is lower than a concentration of the magnesium of the flow channel forming member at a plate thickness center thereof.   
     
     
         5 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein the flow channel forming member includes:
 a core material layer; and   a cladding layer located on one side of the core material layer, the cladding layer excluding brazing material,   wherein the heat transfer member includes a brazing material layer,   wherein the cladding layer is joined to the brazing material layer,   wherein a concentration of the magnesium in a surface layer of the cladding layer is lower than the concentration of the magnesium of the flow channel forming member at the plate thickness center thereof.   
     
     
         6 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein the flow channel forming member includes:
 a core material layer; and   a cladding layer located on one side of the core material layer, the cladding layer excluding brazing material,   wherein the heal transfer member includes a brazing material layer,   wherein the cladding layer is joined to the brazing material layer,   wherein the concentration of the magnesium in the surface layer of the cladding layer is from 0% or more to 0.1% or less by mass.   
     
     
         7 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein one of the flow channel forming member and the heat transfer member includes a core material layer and the brazing material layer,
 wherein the other one of the flow channel forming member and the heat transfer member includes a bare member, a core member of the bare member being exposed,   wherein the brazing material layer and the bare member are joined together,   wherein a concentration of the magnesium of the other one of the flow channel forming member and the heat transfer member at its plate thickness center is from 0% or more to 0.1% or less by mass.   
     
     
         8 . The aluminum alloy heat exchanger as claimed in  claim 1 , wherein zinc is added to a surface of the flow channel forming member,
 wherein a potential difference of 50 mV or more is created in the flow channel forming member in the thickness direction of the flow channel forming member.   
     
     
         9 . A method of manufacturing the heat exchanger as claimed in  claim 1 , the method comprising the steps of:
 assembling components into the heat exchanger;   placing an assembly of the heat exchanger in an oxygen concentration ambience lower than the atmosphere at either atmospheric pressure or a pressure higher than atmospheric pressure; and   brazing components of the heat exchanger without coating flux thereon.