Patent ID: 6916386

Claim:
A core wire for a guide wire comprising a body portion having a high rigidity and a tip end portion having a rigidity lower than the rigidity of the body portion, wherein at least part of said core wire is made of a copper-based alloy comprising 3-10 weight % of Al and 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities, wherein said copper-based alloy wire is formed by at least one of hot working and cold working, maintained at a temperature of at least 500° C. and then rapidly quenched, and further subjected to an aging treatment comprising heating the high-rigidity body portion at a temperature of 250°-350° C., heating the tip end portion at a temperature of less than 250°, and an intermediate portion between said body portion and said tip end portion at a temperature continuously or stepwise changing from the heating temperature of said body portion to the heating temperature of said tip end portion, and wherein said copper-based alloy wire comprises a high-rigidity body portion having a hardness of 350-380 Hv, a low-rigidity tip end portion having a hardness of 235-250 Hv, and an intermediate portion having a hardness of 240-290 Hv between said high-rigidity body portion and said low-rigidity tip end portion, said intermediate portion having rigidity continuously or stepwise changing from said high-rigidity body portion to said low-rigidity tip end portion.