Hypotube with enhanced strength and ductility

Abstract

Hypotubes for use with intra-corporal medical devices are fabricated from a stainless steel alloy exhibiting a combination of excellent yield strength with improved ductility as compared to cold worked AISI 304 stainless steel, from which hypotubes are typically fabricated. The stainless steel alloy may have: (1) a nitrogen content, a carbon content, or a combined nitrogen and carbon content that is greater than that allowed in AISI 304 stainless steel, providing an increased concentration of interstitial atoms to stabilize dislocations generated by cold work; and / or (2) a combined nickel and manganese content that is lower than that allowed in AISI 304 stainless steel to reduce the stability of the austenitic structure, enabling a greater percentage of martensite to be stress-induced by a given level of cold work as compared to AISI 304 SS. Following cold working, the alloy may be heat treated to raise its yield strength by strain aging

Description

[0001] Cross References to Related Applications [0002] This application claims priority to US Application No. 13 / 925,559, filed June 24, 2013, the entire contents of which are incorporated herein by reference. Background technique [0003] Hypotubes are used extensively with a variety of intra-corporal medical devices such as rapid exchange balloon catheters, rapid exchange stent delivery catheters, and specialized guidewires containing hollow proximal shafts ( specialtyguidewire). Such a hypotube may be employed, for example, when introducing the device into an intravascular location within the body. [0004] Hypotubes require adequate strength and ductility to resist kinking. For example, commercially available hypotubes are typically formed from AISI 304 stainless steel, typically by seam welding flat strips into tubes and then drawing the welded tubes to the desired final dimensions. Existing hypotubes are prone to kinking, particularly due to their very thin wall thi...

AI Technical Summary

Problems solved by technology

Increasing the level of cold working increases the strength of the material, but at the same time reduces its ductility (eg, elongation to failure)

Thus, while hypotubes that have been cold worked to increase strength are initially less prone to initiating kinks, once kinks do begin, the reduced ductility makes the hypotube more susceptible to fracture during the initial kink event or upon subsequent realignment

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