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Model No: Nitinol
Nitinol Wire
The most critical performance characteristic of Nitinol medical devices is not strength, but fatigue life. Does your guidewire need to bend 100,000 times inside the blood vessel without breaking? Does your stent need to withstand hundreds of millions of heartbeats? Feel free to inquire.
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Product Introduction
Nitinol wire is not a shape memory alloy wire that can be purchased and used immediately. In fact, you could say that the alloy wire you buy is only a"semi-finished product".
Its superelasticity, its shape memory, and whether it can survive 100,000 cycles in your device depend on:
- Whether the Af temperature is selected correctly
- Whether the surface condition matches your subsequent processes
- Whether the purity is sufficient (how many non-metallic inclusions there are)
- How you plan to process it—welding? crimping? knotting? coiling?
This isn't an ordinary material; it's a"smart material."
If you just want a conductive, flexible, and unbreakable stainless steel wire, don't buy Nitinol; it's not worth the high price.
However, Nitinol is the only choice if you encounter the following situations:
- Your medical device needs to open narrow blood vessels inside the body, and you can't use balloons (self-expanding stents)?
- Your orthodontic archwire needs to apply continuous, gentle force, instead of being"tight at first, then loose after two weeks"like stainless steel?
- Do you need your drive components to automatically deform at specific temperatures without requiring motors or electromagnets (thermal actuators)?
- Do you need your antennas to withstand 1000 bends without deforming and spring back to their original shape (cell phone/walkie-talkie antennas)?
Lork Group supplies Nitinol filaments that strictly conform to ASTM F2063 standards, accompanied by a complete material report (CMTR) including measured Af temperature, tensile properties, and purity rating. Choosing the right material and making the right product are fundamental.
Chemical Composition
The chemical composition of Nitinol is not something that can be"approximately"determined. Even a slight deviation in the nickel-to-titanium ratio can cause the Af temperature to drift by several degrees. More importantly—the impurity content.
The Nitinol filaments supplied by Lork Group strictly conform to ASTM F2063 medical alloy standards:
| Material Type | C | Co | Ni | O+N | Fe | Cu | Ti |
|---|---|---|---|---|---|---|---|
| Content (wt%) | < 0.050 (500 ppm max) | < 0.050 (500 ppm max) | 54.5 - 57.0 | < 0.050 (500 ppm max) | < 0.050 (500 ppm max) | < 0.010 (100 ppm max) | Balance |
Two core concepts: hyperelasticity vs. shape memory
In the world of Nitinol medical alloy , there are two types of"personalities."Many people confuse them.
🔹Type 1: Superelastic (SE)
Phenomenon: When bent forcefully at room temperature, it can bend to 8% strain, and springs back to its original shape upon release. Ordinary spring steel will permanently deform after bending by 1%.
Principle: The material is in the austenitic phase at room temperature. Under stress, it transforms into martensite ("stress-induced martensite"), and returns to austenite after unloading.
Requirements: Af temperature below room temperature (usually 0-20℃).
Typical applications: Vascular stents, orthodontic archwires, guidewires, antennas.
One-sentence judgment: If your device only"passively withstands stress"and springs back at operating temperature, without needing heating—buy superelastic (SE) wire.
🔹Type 2: Shape Memory (SME)
Phenomenon: Can be bent into any shape at low temperatures and retains this"temporary shape."Heated to a specific temperature (above Af), it automatically springs back to its original shape.
Principle: At low temperatures, the material is martensite (soft, deformable). After heating, it becomes austenite (hard, recovers its shape memory).
Requirements: Af temperature higher than the operating temperature (typically 40-100℃).
Typical applications: Thermally driven actuators, fire sprinkler valves, temperature control switches, pipe fittings.
In short: If your equipment requires heat-triggered deformation without external force—buy shape memory (SME) wire.
Mechanical Properties
Many people who are new to Nitinol ask: What is its tensile strength?
The answer is: It depends on the condition, and"strength"is not the key factor.
The answer is: It depends on the condition, and"strength"is not the key factor.
🔹 Cold Worked (CW)
This is the original state after drawing, before the final heat treatment.
This is the original state after drawing, before the final heat treatment.
| Performance | Typical Values | Description |
|---|---|---|
| Tensile strength | ≥ 1380 MPa (≥ 200 ksi) | Very high, but not yet the final product. |
| Elongation | ≥ 4% | Very brittle. You're buying CW condition so you can heat-treat it yourself. |
Application: Intermediate product; customers wind the springs themselves, perform heat treatment, and adjust Af.
🔹 Superelastic Straight Annealed (SE)
This is the state after final heat treatment; the finished product is ready to use.
This is the state after final heat treatment; the finished product is ready to use.
| Performance | Typical Values | Description |
|---|---|---|
| Tensile strength | ≥ 1240 MPa（≥ 180 ksi） | It's already quite sturdy. |
| Elongation at break | >10% | Much tougher than CW state. |
| Loading platform stress | ≥ 480 MPa (≥ 70 ksi, at 4% strain) | This is a key indicator of hyperelasticity—how much force is required to bend to 4%. |
| Unloading platform stress | ≥ 140 MPa (≥ 20 ksi, at 4% strain) | Force during rebound – determines the “softness of rebound”. |
| Permanent Deformation | < 0.5% (unloaded after reaching 8%) | Bends 8% and then releases, leaving less than 0.5% permanent deformation. |
🔹 Key understanding: Platform stress
The hyperelasticity curve of medical alloy Nitinol Wire is not a straight line, but a"plateau"—after the stress reaches a certain value, further increases in strain do not significantly alter the stress. The height and width of this"plateau"determine the"magnitude of force"your product experiences in actual use.
- Orthodontic archwires: Require low plateau stress (gentle force), otherwise, patients will experience toothache.
- Strents: Require appropriate plateau stress (force to open blood vessels); too weak and they won't hold, too strong and they'll puncture blood vessels.
What Lork can do: We can provide complete tensile curves, indicating the loading plateau, unloading plateau, and residual deformation. This data is far more useful than"tensile strength."
Purchase Recommendations
When purchasing Nitinol Wire, it's not about choosing"specifications,"it's about choosing"configurations."Please check which category applies to you:
Scenario 1: You need to make a self-expanding stent/vascular implant
- Requirements: Hyperelasticity, biocompatibility, high fatigue life
- Recommended specifications: SE state, Af 20-35℃ (hyperelastic at body temperature), EMP surface, high purity (HP) grade
- Standard: ASTM F2063 (medical grade)
⚠️ Note: Medical grade and industrial grade are not the same thing. Medical grade requires control over impurities, surface finish, and biocompatibility. Lork Group can provide ISO 13485 certified medical grade materials.
Scenario 2: You need orthodontic archwires
- Requirements: Highly flexible, low plateau stress (gentle force), smooth surface
- Recommended specifications: SE state, Af 10-25℃, E or EMP surface
⚠️ Note: Different stages of orthodontic treatment require different force values. Initial consultations require low force (~200MPa), while fine-tuning requires high force (~400MPa). We can adjust the plateau stress according to your needs.
Scenario 3: You need to make a heat-driven actuator (temperature control switch, valve)
- Requirements: Shape memory effect, specific Af temperature
- Recommended specifications: SME state, Af as per design requirements (usually 50-100℃), cold-worked (CW) state or annealed state
⚠️ Note: Af temperature is the"trigger temperature". If you need 70℃ deformation, Af cannot be 60℃ (not yet fully deformed), nor can it be 90℃ (never changing). Tolerance recommendation: ±5℃.
Scenario 4: You need to make guide wire/braided structures
- Requirements: Extremely fine diameter, ultra-elastic, and smooth
- Recommended specifications: SE state, Af 0-20℃, E or EMP surface, diameter 0.025-0.2mm
⚠️ Note: The torque transmission characteristics of the ultra-fine filament are very important. Before purchasing, confirm whether you need"core filament"(high pushability) or"braided filament"(high smoothness).
Scenario 5: You need to make industrial springs / antennas / eyeglass frames
- Requirements: Highly elastic, corrosion-resistant, inexpensive
- Recommended specifications: SE state, Af 0-20℃, LO or DK surface, industrial grade (non-medical)
⚠️ Note: Industrial grade is 30-50% cheaper than medical grade. If your product does not come into contact with the human body and does not require extremely high fatigue life, there is no need to buy medical grade.
Contact Us
Choosing the wrong Nitinol is a waste of money. Send us your usage scenario, temperature, and fatigue requirements, and our materials engineers will help you with"selection and matching"—free of charge.
📞 Hotline: [+86 175 1308 1871]
📧 Email: [daisy@lorkgroup.com]
💬 WeChat/WhatsApp: [+86 175 1308 1871]
📞 Hotline: [+86 175 1308 1871]
📧 Email: [daisy@lorkgroup.com]
💬 WeChat/WhatsApp: [+86 175 1308 1871]
