Shenzhen Wuge Industrial Co., Ltd

There are significant differences in composition and properties between nickel titanium memory alloy wire and stainless steel wire. The following is a comparative analysis of the core differences between the two from multiple dimensions:

1、 Composition and Structure

Basic components: Nickel titanium memory alloy wire is made of nickel (Ni) and titanium (Ti), with a ratio usually close to 1:1 (such as Ni55Ti45). Stainless steel wire is based on iron (Fe) and contains elements such as chromium (Cr, ≥ 10.5%), nickel (Ni), molybdenum (Mo), etc. (such as 304 stainless steel: Fe+18% Cr+8% Ni).

Crystal structure: Nickel titanium memory alloy wire has a shape memory effect and a hyperelastic martensitic austenite transformation structure, which can be adjusted by heat treatment to regulate the transformation temperature (such as triggering the memory effect at body temperature). The crystal structure of stainless steel wire is stable, without memory effect, and requires external force recovery after deformation (austenitic stainless steel such as 304 is non-magnetic, while ferritic/martensitic stainless steel has magnetism).

Production process: requires precise control of melting temperature (above 1500 ℃), cold drawing process, and aging treatment (endowing memory performance), making processing difficult. And the stainless steel wire technology is mature, which can be formed by hot rolling and cold drawing, and the surface treatment (such as polishing and coating) is simple.

Nickel titanium memory alloy wire

2、 Key performance comparison

1. Mechanical properties

(1) Nickel titanium memory alloy wire:

Super elasticity: can stretch 8%~10% without permanent deformation (ordinary metals only 0.1%~0.3%), automatically returns to its original state after external force is removed, suitable for dynamic load scenarios.

Memory effect: At a specific temperature (such as body temperature of 37 ℃), it can recover from a temporary shape to the original shape of "memory", used for structures that require automatic reset.

Strength: The tensile strength is about 800-1200 MPa, lower than high-strength stainless steel (such as 304 stainless steel at about 520 MPa, but martensitic stainless steel can reach over 1000 MPa), but the elastic modulus is low (about 40-80 GPa, stainless steel at about 200 GPa), and it is more prone to bending deformation.

(2) Stainless steel wire:

High strength and hardness: Martensitic stainless steel (such as 420 stainless steel) can reach a hardness of HRC 50 or above, suitable for wear-resistant scenarios.

Strong rigidity: High elastic modulus, requiring external force to reset after deformation, suitable for structures that require stable support (such as building steel bars and mechanical springs).

2. Physical characteristics

(1) Nickel titanium memory alloy wire:

Low density: about 6.4-6.5 g/cm ³, more than 20% lighter than stainless steel (stainless steel is about 7.9 g/cm ³), suitable for lightweight requirements.

Non magnetic (austenitic state): Non magnetic in the austenite phase at room temperature, suitable for medical and electronic equipment anti magnetic interference scenarios.

Temperature sensitivity: The phase transition temperature (such as Af temperature) determines the triggering conditions of the memory effect and needs to be designed according to the usage environment (such as medical alloy Af ≈ 34 ℃, close to body temperature).

(2) Stainless steel wire:

High density: Due to its large weight, it is not suitable for lightweight scenarios.

Magnetic difference: Austenitic stainless steel (such as 304, 316) is usually non-magnetic, while ferritic/martensitic stainless steel (such as 430, 410) has magnetism and can be used in electromagnetic equipment.

Good thermal stability: The strength decreases slowly at high temperatures (such as 310S stainless steel, which can withstand high temperatures up to 1200 ℃), making it suitable for high-temperature environments.

3. Corrosion resistance

(1) Nickel titanium memory alloy wire:

The surface naturally forms a dense TiO ₂ oxide film, which has strong resistance to body fluids, blood, and acid-base corrosion, superior to most stainless steels, especially suitable for human environments or highly corrosive media (such as seawater and chemical solutions).

Excellent biocompatibility, no risk of metal ion precipitation, in compliance with medical ISO 58321 standard.

(2) Stainless steel wire:

Relying on Cr ₂ O ∝ passivation film for corrosion resistance, it performs well in conventional environments such as atmosphere and water. However, pitting corrosion or stress corrosion may occur in chloride containing ions (such as seawater, sweat) or strong acid-base environments (such as 304 stainless steel that is not resistant to concentrated hydrochloric acid and requires 316L stainless steel).

Medical grade stainless steel (such as 316L) requires additional control of carbon content (≤ 0.03%) to reduce corrosion risk, but long-term implantation may still result in the release of trace amounts of metal ions.

Stainless steel wire

4. Processing and Cost

(1) Nickel titanium memory alloy wire:

Complex processing: Multiple annealing is required to eliminate cold working stress, and memory performance is adjusted through aging treatment (such as insulation at 450-550 ℃), resulting in high production costs.

Expensive prices: The cost of raw materials (nickel, titanium) is 3-5 times that of stainless steel, and the price of finished wire is usually 5-10 times that of stainless steel (such as about 200 yuan/meter for Φ 1mm nickel titanium wire and about 20 yuan/meter for 304 stainless steel wire).

(2) Stainless steel wire:

Convenient processing: The diameter can be directly controlled through cold drawing, and the surface treatment (such as coating and polishing) is mature, suitable for large-scale production.

Low cost: abundant raw materials (iron, chromium), mature industrial production, high cost-effectiveness.

In summary, there are differences in composition and properties between nickel titanium memory alloy wire and stainless steel wire. The characteristics of both determine the application scenario, and the selection should be based on actual needs.