Aluminum alloy fin stock for heat exchangers having excellent strength, electric conductivity, corrosion resistance and brazability, and heat exchanger

Abstract

Provided is an aluminum alloy fin stock for a heat exchanger which is free from brazing defects due to fin deformation during brazing and is excellent in strength, electric conductivity, corrosion resistance, and brazability, and a heat exchanger. An aluminum alloy fin stock for a heat exchanger is made of an aluminum alloy having a composition including, by mass %, Mn: 1.2% to 2.0%, Si: 0.5% to 1.3%, Cu: 0.001% to less than 0.05%, Fe: 0.1% to 0.5%, Zn: 0.5% to 2.5%, and a balance consisting of Al and inevitable impurities, in which, at a room temperature after brazing heating, the aluminum alloy fin stock has a tensile strength of 140 MPa or more, a 0.2% proof stress of 50 MPa or more, a electric conductivity of 42% IACS or more, an electric potential of −800 mV or more and −710 mV or less, and a corrosion weight loss of 120 mg/dm2 or less after 16 weeks in a neutral salt spray test.

1 . An aluminum alloy fin stock, wherein the aluminum alloy fin stock is made of an aluminum alloy having a composition comprising, by mass %,
 Mn: 1.2% to 2.0%,   Si: 0.5% to 1.3%,   Cu: 0.001% to less than 0.05%,   Fe: 0.1% to 0.5%, Zn: 0.5% to 2.5%, [[and]]   Al, and   inevitable impurities,   wherein, at a room temperature after brazing heating, the aluminum alloy fin stock has a tensile strength of 140 MPa or more, a 0.2% proof stress of 50 MPa or more, an electric conductivity of 42% IACS or more, an electric potential of −800 mV or more and −710 mV or less, and a corrosion weight loss of 120 mg/dm 2  or less after 16 weeks in a neutral salt spray test.   
     
     
         2 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy further comprises, by mass %:   Ti: 0.01% to 0.20%,   Cr: 0.01% to 0.20%,   Mg: 0.01% to 0.20%, and   Zr: 0.01% to 0.20%.   
     
     
         3 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy has a composition satisfying
   2.1≤[Mn content (mass %)]+[Si content (mass %)]+7.5×[Cu content (mass %)]≤3.4, and   Relational Expression (i):
 
   [Zn content (mass %)]−18.8×[Cu content (mass %)]≥0.2.   Relational Expression (ii):
 
   
     
     
         4 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy fin stock has an average grain size of 100 μm or more and less than 2000 μm after brazing heating.   
     
     
         5 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy fin stock has a 0.2% proof stress in a range of 15 to 40 MPa at each temperature in a range of 400° C. to 550° C.   
     
     
         6 . The aluminum alloy fin stock according to  claim 1 ,
 wherein, before brazing heating, a number density of Al—Mn-based, Al—Mn—Si-based, and Al—Fe—Si-based second phase compounds having an equivalent circle diameter of 0.01 to 0.10 μm is 1.0×10 5  points/mm 2  or more, and   a metallographic structure is a fibrous grain structure.   
     
     
         7 . The aluminum alloy fin stock according to  claim 1 ,
 wherein, after brazing heating, Al—Mn-based, Al—Mn—Si-based, and Al—Fe—Si-based second phase compounds having an equivalent circle diameter of 0.01 to 0.10 μm are present in 1.0×10 4  points/mm 2  or more, and   Al—Fe-based crystallized compounds having an equivalent circle diameter of 1.0 μm or more and Al—Cu-based second phase compounds having an equivalent circle diameter of 0.05 μm or more are present in 1.0×10 3  points/mm 2  or less.   
     
     
         8 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy fin stock has a sheet thickness of 100 μm or less.   
     
     
         9 . The aluminum alloy fin stock according to  claim 1 ,
 wherein the aluminum alloy fin stock has a corrosion current density of 0.05 mA/cm 2  or less.   
     
     
         10 . The aluminum alloy fin stock according to  claim 1 ,
 wherein, before brazing heating, the aluminum alloy fin stock has a tensile strength at a room temperature of 250 MPa or less, and a 0.2% proof stress at a room temperature of 230 MPa or less.   
     
     
         11 . The aluminum alloy fin stock according to  claim 1 ,
 wherein, before brazing heating, the aluminum alloy fin stock has a recrystallization completion temperature of 450° C. or lower.   
     
     
         12 . A heat exchanger comprising the aluminum alloy fin stock according to  claim 1 .