Shape memory alloy, super elastic nickel titanium alloy, Nitinol wire for biomedicine

PRODUCT

Shape memory alloy, super elastic nickel titanium alloy, Nitinol round wire, flat wire, shaped cross sectional wire for biomedicine

OVERVIEW

Nitinol are the most comprehensively studied and best shape memory alloys. They have the characteristics of high strength, high plasticity, good corrosion resistance, good stability and excellent biocompatibility. The superiority of its application in medicine is that other shape memory alloys can not be replaced.

Nitinol combines two closely related unique characteristics: shape memory and superelasticity. Shape memory gives Nitinol the ability to be deformed at one temperature, and then return to its original shape when being heated to its transformation temperature. This effect is caused by the material changing from its low temperature monoclinic martensitic structure to the high temperature cubic austenitic structure.

PROPERTIES OF NITINOL

1 Shape memory

2 Super elastic

3 Sensitivity to changes in oral temperature

4 Good corrosion resistance

5 Toxin immunity

6 Gentle corrective force

7 Good shock absorption characteristics

NITINOL FOR BIOMEDICINE APPLICATION

Nitinol is a term for binary near equal-atom Ni-Ti alloys, and it is widely used in medical due to its unique super-elasticity. However, Ternary or other Nickel-Titanium alloys can be achieved for different properties.

For biomedicine, nitinol archwire is used for the early alignment of patients' teeth. Nitinol push spring and tension spring are springs used for orthodontic teeth, scoliosis orthopedic device. In addition, nitinol was used in surgery to make various bone connector, blood vessel clip, coagulation filters, blood vessel dilation components, all kinds of intracavitary stent, embolization device, heart patch, thrombus filters, interventional guide wires and surgical sutures, etc.

CHEMICAL COMPOSITION

Table 1

The chemical composition is as per ASTM F2063-12 or GB 24627-2009(wt%)

NITINOL WIRE

Shape memory Nitinol wire can be used to develop implants that may be delivered into the body in a compact shape and then activated into their functional form once they have been deployed. If you need the wire to be in a certain shape for a particular application, we offer Shape Setting. This “sets” a wire shape that specifically conforms to your device design requirements. Not only do we manufacture Nitinol in various forms, we control the entire process, from start to finish, by being the world's leading melt-to-finish source for Nitinol to the medical device industry.

Superelasticity occurs at temperatures just above the transformation temperature and allows the material to recover from up to 8% strain with a permanent set of 0.5% or less.

Nitinol is available from in two basic forms:

Nitinol round wire and flatwire

Nitinol centerless ground bar

All Nitinol grades are available in either cold worked condition ready for heat treatment or as straightened super-elastic wire.

NITINOL WIRE SPECIFIC APPLICATION

Nitinol wire is used for many different medical and industrial applications. Medical application include vascular therapy, cardiac rhythm management, neurostimulation, orthodontic, orthopaedic, endoscopy, implant dentistry, etc. Typical medical application include guide wire, woven support, dental root file, dental arch wire, iud, suture line, etc

Some typical engineering applications for each Nitinol medical grades are given below:

Nitinol A: Guidewires, stents, stylets, forming mandrels, stone retrieval baskets, orthodontic files, etc.

Nitinol B*: Often used in applications that require a high loading and unloading plateau stress at room temperature. Chromium doped for decreased transformation temperature and increased tensile strength.

Nitinol C**: Applications requiring increased stiffness. Cobalt doped for decreased transformation temperature and increased tensile strength.

Nitinol D: Provides the best cycling performances at body temperature (37°C).

Nitinol E: A common application for this alloy is high temperature actuators.

Nitinol F: A common application for this alloy is high temperature actuators.

Nitinol G: Typically used in applications that require a phase transformation at body temperature (37°C).

Nitinol H: For use in very cold temperature environment applications.

* Typical chemical composition: ASTM F2063 Exc. Cr 0.2% to 0.3%

** Typical chemical composition: ASTM F2063 Exc. Co 1% to 2%

MECHANICAL PROPERTIES OF SUPERELASTIC ALLOYS

Table 2: Cold worked super elastic

MECHANICAL PROPERTIES OF SHAPE MEMORY ALLOYS

Table 3: Cold worked shape memory

NITINOL WIRE FORMS

Round wire: 0.05 to 4.0mm

Flat wire – aspect ratio: W/T < 10

Rolled Strip – aspect ratio: W/T >10:1

Minimum Thickness: 0.008mm

Maximum Width: 11.5mm

Turkshead: Square, Rectangular

Custom Shapes: A wide variety of shaped cross-sectional wire

Nitinoal round wire diameter and tolerance

Table 4

Out of roundness within half of the diameter tolerance.

DELIVERY CONDITION

(1) Straightened superelastic(SE)

(2) Cold worked (CW)

WIRE SURFACE CONDITION

(1) Light Oxide - diamond drawn surface

(2) Dark Oxide - diamond drawn surface

(3) Black Oxide - diamond drawn surface

(4) Etch – chemical removal of oxide layer - will retain smooth surface

(5) Pickled – chemical removal of oxide layer along with a slight amount of base metal - surface will have a rough texture

(6) Etched and Mechanically Polished – Chemical removal of oxide layer followed by mechanical polish - surface will have stainless steel appearance (although at >40x magnification, micro scratches will be present

(7) Oxide free – smooth and without visible oxide

WIRE CODE

Active af temperature is one of the critical properties of Nitinol that can determine the effective super-elastic performance of the alloy. Although all the major Ni content in the range of 54.5~57.0mass% conforms the ASTM F2063-12 standard spec, its A_f is very sensitive to the chemical composition, detailed grading of Nitinol composition is of crucial importance. This is why we use detailed and verified material code to identify the alloy.

Table 5

NITINOL CENTERLESS GROUND BAR

Along with Nitinol wire, medical grade Nitinol bar also available with diameters range from 2.0mm to 5.0mm with the option of a natural forming oxide or centerless ground and polished surface.

TYPICAL MECHANICAL PROPERTIES OF GROUND BAR

Condition: Super elastic

Table 6

MAIN APPLICATIONS

Orthopaedic

Orthodontic

STANDARD SPECIFICATION

ASTM F2063-12 Standard chemical composition of a wrought nitinol shape memory alloy used in medical devices and surgical implants

GB 24627 Standard chemical composition of a wrought nitinol shape memory alloy used in medical devices and surgical implants

ASTM F2633-13 Standard specification for seamless nitinol shape memory alloy fitting for medical devices and surgical implants

ASTM F2005-05 Standard terminology for nitinol shape memory alloys

ASTM F2004-05 A standard test method for the transition temperature of Nitinol alloy by thermal analysis

ASTM F2516-14 Tensile test method for nitinol hyperelastic materials

ASTM F2082-15 The standard test method for phase transition temperature of nitinolshape memory alloy by bending and free restoration.

ADVANTAGE

All incoming Nitinol raw materials are subjected to third party inspection to ensure they meet proprietary specifications for chemistry, transformation temperature, material homogeneity, and microstructure. To promote an exceptionally smooth and uniform surface finish quality, all wire and tube products utilize a high precision single and or multi-crystalline diamond drawing die technology. After the correct super-elastic heat treatment, medical grade nickel-titanium materials can undergo up to 8% strain without permanent bending at human temperature.

BUSINESS TERM

NOTE:

More information available from our official web site http://www.cmmetal.cn

With background of more than 50 years of material R&D experience, CMMC is a high-tech enterprise specialized in production of high temperature alloys, corrosion resistant alloys, precision alloys, wear resistant alloys, refractory alloys and other special alloys.

With main smelting equipments by CONSARC, including vacuum induction melting furnace (VIM 3 metric tons x 1 set), inert gas protective electric slag remelting furnace (IG-ESR 5 metric tons x 1 set, 10 metric tons x 2 sets), vacuum arc remelting furnace (VAR 10 metric tons x 1 set), CMMC has an annual production capacity of 3000 metric tons.

Established in 2016, CMMC stll having an investing plan of more than 30 million U.S.Dollars in the coming 5 years. CMMC aspires to become an internationally renowned supplier and leading brand of key materials for core components of high-end equipments in the application fields of aerospace, clean energy, petroleum, chemical engineering, medical, marine engineering, food and automobile, etc.

Our main products include forgings, bars, rods, tubulars, plates, sheets, strips, wire rods, precision wires, etc.

From ultra-pure smelting,  hot and cold forming, heat treatment, mechanical processing to finish machining, CMMC provides the whole process of one-stop professional services.

From demand idea to research and development, from technology innovation to promoting of products upgrading, from customer's puzzles and difficulties to final solution, from smelting to market, no matter wherever, whenever, whatever and however, CMMC always try to provide satisfactory one-stop service.

By providing better materials to make a better world, CMMC never give up the dream.