Guide wire

Abstract

A guide wire includes a wire body having a first wire disposed at a distal end and a second wire joined to a proximal end of the first wire at a joint by welding. The joint is curved. In the joint, at least one component (e.g., Ti) of the material of the first wire decreases toward the proximal end and at least one component (e.g., Fe) of the material of the second wire decreases toward the distal end. When a tensile test is conducted on a region of the wire body including the joint, the region of the wire body has, in a tensile load and elongation diagram, an elastic section extending substantially straight upwardly to the right, a yield section extending substantially horizontally or upwardly to the right from the elastic section, and a substantially straight section extending upwardly to the right from the yield section.

1 . A guide wire comprising:
 a wire body having a filamentary first wire disposed at a distal end of the guide wire and a filamentary second wire joined to a proximal end of the first wire through a weld joint;   wherein the first wire is made of a Ni—Ti base alloy and the second wire is made of a Fe—Cr—Ni base alloy, and concentrations of Ni, Ti and Fe are in the weld joint;   wherein the concentrations of Ni and Ti in the weld joint have a first concentration gradient gradually decreasing adjacent the first wire toward a proximal end of the guide wire, a second concentration gradient gradually decreasing adjacent the second wire toward the proximal end of the guide wire, and a third concentration gradient positioned between the first and second concentration gradients and steeper than the first and second concentration gradients; and   the concentration of Fe in the weld joint has a first Fe concentration gradient gradually decreasing adjacent the second wire toward a distal end of the guide wire, a second Fe concentration gradient gradually decreasing adjacent the first wire toward the distal end of the guide wire, and a third Fe concentration gradient positioned between the first and second Fe concentration gradients and steeper than the first and second Fe concentration gradients.   
     
     
         2 . A guide wire according to  claim 1 , wherein the concentrations of Ti and Fe in the weld joint are mixed with each other only in an area of the third concentration gradients. 
     
     
         3 . A guide wire according to  claim 1 , wherein the wire body extends in an axial direction from a proximal end of the wire body to a distal end of the wire body, and a length of the third Fe concentration gradient in the axial direction is shorter than each of the lengths of the first and second Fe concentration gradients in the axial direction. 
     
     
         4 . A guide wire according to  claim 1 , wherein the wire body extends in an axial direction from a proximal end of the wire body to a distal end of the wire body, and a length of the third concentration gradient of Ni and Ti in the axial direction is shorter than each of the lengths of the first and second concentration gradients of Ni and Ti in the axial direction. 
     
     
         5 . A guide wire according to  claim 1 , wherein a concentration of Cr is in the weld joint, and the concentration of Cr in the weld joint has a first Cr concentration gradient gradually decreasing adjacent the second wire toward a distal end of the guide wire, a second Cr concentration gradient gradually decreasing adjacent the first wire toward the distal end of the guide wire, and a third Cr concentration gradient positioned between the first and second Cr concentration gradients and steeper than the first and second Cr concentration gradients. 
     
     
         6 . A guide wire according to  claim 1 , wherein the second wire has an elastic constant greater than an elastic constant of the first wire. 
     
     
         7 . A guide wire according to  claim 1 , wherein said joint has a curved shape that is one of a dish shape, a spherical shape and a parabolic shape.