Shape-setting refers to the process used to form a Nitinol wire, tube or sheet into a specific and often complex geometry. Whether the Nitinol alloy is to be used in the superelastic or shape memory condition, it is necessary to establish the appropriate heat treatment. This is done by carefully constraining the material into its new shape using a specially designed fixture or mandrel followed by a defined heat treatment. Multiple shaping operations may be necessary if the part is particularly complex or to prevent cracking/fracture of high strain regions.
Memry has extensive experience in shape-setting Nitinol components. Our engineering team will work closely with you to achieve the desired geometrical and thermo-mechanical specifications. For each application, our team chooses from the following heat treatment methods, each offering a different mix of control and speed balanced against device requirements and cost:
Molten Salt Bath heat treatment consists of immersing the constrained wire, tube, strip or sheet shape into a temperature controlled bath of molten salt. Molten salt offers the greatest thermal conductivity of all methods, which allows for consistent heat absorption and fast process times.
Fluidized Bed heat treatment consists of immersing the constrained wire, tube, strip, or sheet shape into a temperature controlled, volume of fluidized sand. Fluidized sand is an ideal method for both large geometries (in excess of 24”) and small geometries with blind features that could trap other media.
Air Furnace heat treatment consists of soaking the constrained wire, tube, strip, or sheet shape in a temperature controlled atmosphere. Air furnace is an ideal method intricate, small part geometries where intrusion of the heat treating media is a concern.
Heated Die heat treatment consists of constraining the wire, tube, strip or sheet shape in a heated, temperature controlled mold. Heated die treatment offers the ability to locally shape-set a portion of component without impacting adjacent material properties. Moreover, deformation under heat allows for shape-setting of higher strain geometries in a single process step.
Air Convection Furnace heat treatment consists of soaking the constrained wire, tube, strip, or sheet shape in a temperature controlled, forced convection atmosphere. Circulation of the heat treatment atmosphere improves temperature uniformity and stability.