Guide wire with core having welded wire segments
An intravascular guide wire having two core materials joined together without the use of a connector tube or sleeve, the core materials being stainless steel and pseudoelastic metal alloy, nitinol. The core materials are joined to each other through an intermediate transition piece made essentially of nickel, which is welded on either side to the two core materials. In a multi-segment intravascular guide wire, discrete, high modulus and medium modulus core portions of different materials are welded to a shapeable, low modulus distal core portion made of a third material having a flattened, shapeable section at a most distal end that is not welded to but made from the distal core portion, so the flattened, shapeable section can be deformed to create a steerable tip. Processes such as simultaneous resistance and friction welding can be used to join the core portions.
1. A method for joining a multi-segment core intravascular guide wire, comprising the ordered steps of:
providing multiple, discrete portions of the guide wire core made from different materials;
axially aligning the discrete core portions;
rotating one portion at a fixed speed;
butting two core portions together while applying a fixed axial force creating upset material to create joined core portions with a butt joint;
increasing rotation speed of the joined core portions;
increasing axial force;
increasing resistance weld energy;
holding resistance weld energy constant;
decreasing resistance weld energy; and
decreasing rotational speed to zero.
2. The method of claim 1 , wherein increasing resistance weld energy occurs while the joined core portions are rotated.
3. The method of claim 1 , wherein the method further comprises removing the upset material from the periphery of the butt joint of the joined core portions.
4. The method of claim 3 , wherein removing the upset material from the periphery of the butt joint includes grinding the upset material.
5. The method of claim 3 , wherein removing the upset material from the periphery of the butt joint includes passing the joined core portions through a die to shear away the upset material.
6. The method of claim 1 , wherein the resistance weld energy is terminated and rotational speed of the core portions is stopped abruptly.