Tube member having excellent local bendability, and method for manufacturing same

A method for manufacturing a tube member used as a surgical instrument for a paranasal sinus, the method comprising:

• cold-working a shape-memory alloy into a tubular shape to prepare a straight tube member having a first region, a second region, and a third region;
• bending at least a portion of the second region of the tube member to a predetermined angle;
• subjecting an entire tube member to a first heat treatment at a first heating temperature to transform the entire tube member into an austenite phase;
• locally subjecting the second region of the tube member to a second heat treatment at a second heating temperature to transform the second region into a martensite phase;
• locally cooling the third region of the tube member to a temperature lower than a first phase transformation temperature;
• expanding one end of the cooled third region and coupling a cutting member thereto;
• and
• raising a temperature of the third region to a temperature higher than the first phase transformation temperature,
• wherein each of the first region, the second region, and the third region have a respective phase transformation temperature at which a phase transformation from a low temperature martensite phase to a high temperature austenite phase occurs,
• wherein the first heat treatment and the second heat treatment are performed to allow heat-treated regions to undergo phase transformations from the low temperature martensite phase to the high temperature austenite phase,
• wherein a second phase transformation temperature of the second region is higher than a working temperature at which the bending of the at least a portion of the second region is performed, and
• wherein the second region is configured to:
• retain a bent shape in the martensite phase at the working temperature, and
• upon being heated to a temperature higher than the working temperature, undergo phase transformation to the austenite phase and recover a pre-bent shape, exhibiting a shape memory behavior.