High strength and high thermal conductivity copper alloy tube and method for producing the same

Abstract

A high strength and high thermal conductivity copper alloy tube contains: Co of 0.12 to 0.32 mass %; P of 0.042 to 0.095 mass %; and Sn of 0.005 to 0.30 mass %, wherein a relationship of 3.0≦([Co]−0.007)/([P]−0.008)≦6.2 is satisfied between a content [Co] mass % of Co and a content [P] mass % of P, and the remainder includes Cu and inevitable impurities. Even when a temperature is increased by heat generated by a drawing process, a recrystallization temperature is increased by uniform precipitation of a compound of Co and P and by solid-solution of Sn. Thus, the generation of recrystallization nucleuses is delayed, thereby improving heat resistance and pressure resistance of the high strength and high thermal conductivity copper alloy tube.

1 . A high strength and high thermal conductivity copper alloy tube subjected to a drawing process, wherein the copper alloy tube has an alloy composition comprising:
 Co of 0.12 to 0.32 mass %;   P of 0.042 to 0.095 mass %; and   Sn of 0.005 to 0.30 mass %,   wherein a relationship of 3.0≦([Co]−0.007)/([P]−0.008)≦6.2 is satisfied between a content [Co] mass % of Co and a content [P] mass % of P, and the remainder includes Cu and inevitable impurities.   
     
     
         2 . (canceled) 
     
     
         3 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein the alloy composition further comprises at least one of Zn of 0.001 to 0.5 mass %, Mg of 0.001 to 0.2 mass %, and Zr of 0.001 to 0.1 mass %. 
     
     
         4 . (canceled) 
     
     
         5 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the drawing process is 50% or less, or a recrystallization ratio of a heat-influenced portion subject to the drawing process is 20% or less. 
     
     
         6 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein a value of Vickers hardness (HV) of a drawing-processed portion subjected to the drawing process after heating at 700° C. for 20 seconds is 80% or more of a value of Vickers hardness (HV) before the heating. 
     
     
         7 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein the drawing process is a spinning process, and
 wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the spinning process is 50% or less.   
     
     
         8 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein the drawing process is a cold-drawing process, and
 wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the cold-drawing process is 50% or less, or a recrystallization ratio of a heat-influenced portion subject to the cold-drawing process is 20% or less, after brazing with another copper tube at end portions of the drawing-processed portion and the heat-influenced portion.   
     
     
         9 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein a value of (P B ×D/T) is 600 or more, where D (mm) is an outer diameter of a straight tube portion which is not subjected to the drawing process, T (mm) is a thickness, and P B  (MPa) is a burst pressure that is a pressure at the time of bursting the straight tube portion by applying internal pressure. 
     
     
         10 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 ,
 wherein a value of (P 0.5% ×D/T) is 300 or more, where D (mm) is an outer diameter of a straight tube portion which is not subjected to the drawing process, T (mm) is a thickness, and P 0.5%  (MPa) is a 0.5% deformation pressure that is a pressure at the time of deforming the outer diameter by 0.5% by applying internal pressure, or   wherein a value of (P 1% ×D/T) is 350 or more, where P 1%  (MPa) is a 1% deformation pressure that is a pressure at the time of deforming the outer diameter by 1% by applying internal pressure.   
     
     
         11 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein in a metal structure of a process end portion and a process center portion before the drawing process, after the drawing process, or after brazing with another copper tube, substantially circular or substantially oval fine precipitates having a size of 2 to 20 nm containing Co and P are uniformly dispersed, or 90% or more of all precipitates are uniformly dispersed as fine precipitates having a size of 30 nm or less. 
     
     
         12 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein a metal structure of a process center portion subjected to the drawing process is recrystallized, and has a crystal grain diameter of 3 to 35 μm. 
     
     
         13 . The high strength and high thermal conductivity copper alloy tube according to  claim 1 , wherein the copper alloy tube is used as a pressure-resistance and heat-transfer vessel of a heat exchanger. 
     
     
         14 .- 18 . (canceled) 
     
     
         19 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the drawing process is 50% or less, or a recrystallization ratio of a heat-influenced portion subject to the drawing process is 20% or less. 
     
     
         20 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein a value of Vickers hardness (HV) of a drawing-processed portion subjected to the drawing process after heating at 700° C. for 20 seconds is 80% or more of a value of Vickers hardness (HV) before the heating. 
     
     
         21 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein the drawing process is a spinning process, and
 wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the spinning process is 50% or less.   
     
     
         22 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein the drawing process is a cold-drawing process, and
 wherein a recrystallization ratio of a metal structure of a drawing-processed portion subjected to the cold-drawing process is 50% or less, or a recrystallization ratio of a heat-influenced portion subject to the cold-drawing process is 20% or less, after brazing with another copper tube at end portions of the drawing-processed portion and the heat-influenced portion.   
     
     
         23 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein a value of (P B ×D/T) is 600 or more, where D (mm) is an outer diameter of a straight tube portion which is not subjected to the drawing process, T (mm) is a thickness, and P B  (MPa) is a burst pressure that is a pressure at the time of bursting the straight tube portion by applying internal pressure. 
     
     
         24 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 ,
 wherein a value of (P 0.5% ×D/T) is 300 or more, where D (mm) is an outer diameter of a straight tube portion which is not subjected to the drawing process, T (mm) is a thickness, and P 0.5%  (MPa) is a 0.5% deformation pressure that is a pressure at the time of deforming the outer diameter by 0.5% by applying internal pressure, or   wherein a value of (P 1% ×D/T) is 350 or more, where P 1%  (MPa) is a 1% deformation pressure that is a pressure at the time of deforming the outer diameter by 1% by applying internal pressure.   
     
     
         25 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein in a metal structure of a process end portion and a process center portion before the drawing process, after the drawing process, or after brazing with another copper tube, substantially circular or substantially oval fine precipitates having a size of 2 to 20 nm containing Co and P are uniformly dispersed, or 90% or more of all precipitates are uniformly dispersed as fine precipitates having a size of 30 nm or less. 
     
     
         26 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein a metal structure of a process center portion subjected to the drawing process is recrystallized, and has a crystal grain diameter of 3 to 35 μm. 
     
     
         27 . The high strength and high thermal conductivity copper alloy tube according to  claim 3 , wherein the copper alloy tube is used as a pressure-resistance and heat-transfer vessel of a heat exchanger.