Copper-titanium alloys excellent in strength, conductivity and bendability, and method for producing same

Abstract

The present invention provides a titanium copper alloy excellent in strength, electrical conductivity and bendability, characterized in that it consists essentially of 1.5 to 2.3% by mass of Ti, balance Cu and inevitable impurities; said alloy having a 0.2% yield strength of 750 MPa or greater; an electrical conductivity of 17% IACS or greater; and a relationship represented by the formula: MBR/t ≦0.04× YS −30, in which, YS is a 0.2% yield strength (MPa), and MBR/t is a ratio of a minimum bending radius (MBR; mm) for no cracking when said alloy is subjected to W bend test according to JIS H3130 standard along a transverse direction to a rolling direction, to a thickness (t; mm) of test piece.

1 . A titanium copper alloy excellent in strength, electrical conductivity and bendability, consisting essentially of 1.5 to 2.3% by mass of Ti, balance Cu and inevitable impurities; 
 said alloy having a 0.2% yield strength of 750 MPa or greater; an electrical conductivity of 17% IACS or greater; and a relationship represented by the formula:       MBR/t≦ 0.04 ×YS− 30,   in which,    YS is a 0.2% yield strength (MPa), and    MBR/t is a ratio of a minimum bending radius (MBR; mm) for no cracking when said alloy is subjected to W bend test according to JIS H3130 standard along a transverse direction to a rolling direction, to a thickness (t; mm) of test piece.    
     
     
         2 . The titanium copper alloy according to  claim 1 , having an electrical conductivity of 20% IACS or greater.  
     
     
         3 . The titanium copper alloy according to  claim 1 , having a 0.2% yield strength of 800 MPa or greater.  
     
     
         4 . The titanium copper alloy according to any one of the preceding claims; 
 said alloy having Cu—Ti intermetallic compound phases observed in a cross section transverse to the rolling direction whose diameters are 2.0 μm or less; and an area ratio (S; %) of Cu—Ti intermetallic compound phases observed in the cross section transverse to the rolling direction whose diameters are 0.02 to 2.0 μm may have a relationship with Ti content ([Ti]; % by mass) represented by the formula: 8.1×[Ti]−11.5≦S≦7.5; and    said alloy having an average grain size of 2 to 10 μm in the cross section transverse to the rolling direction as measured by JIS H0501 standard intercept method.    
     
     
         5 . A method for producing from an ingot the titanium copper alloy according to any one of  claims 1  to  3 , comprising sequential steps of a hot rolling, a cold rolling, a solution treatment, a cold rolling, and an aging treatment; 
 a reduction ratio of said cold rolling before said solution treatment being 89% or greater,    a heating temperature T (° C.) for said solution treatment being in a range represented by the formula: [6580/{7.35−ln[Ti]}]−333≦T≦[6580/{7.35−ln[Ti]}]−273,    an average cooling rate in said solution treatment being 300° C./s or greater,    a reduction ratio of said cold rolling before said aging treatment being 10 to 70%,    a heating temperature for said aging treatment being 350 to 450° C.,    a heating hold time for said aging treatment being 5 to 20 hours, and    an average cooling rate from the heating temperature for said aging treatment being 10 to 50° C./h.    
     
     
         6 . A method for producing from an ingot the titanium copper alloy according to  claim 4 , comprising sequential steps of a hot rolling, a cold rolling, a solution treatment, a cold rolling, and an aging treatment; 
 a reduction ratio of said cold rolling before said solution treatment being 89% or greater,    a heating temperature T (° C.) for said solution treatment being in a range represented by the formula: [6580/{7.35−ln[Ti]}]−333≦T≦[6580/{7.35−ln[Ti]}]−273,    an average cooling rate in said solution treatment being 300° C./s or greater,    a reduction ratio of said cold rolling before said aging treatment being 10 to 70%,    a heating temperature for said aging treatment being 350 to 450° C.,    a heating hold time for said aging treatment being 5 to 20 hours, and    an average cooling rate from the heating temperature for said aging treatment being 10 to 50° C./h.