Why should I choose 316LVM and who can supply it reliably?
Failure of materials in implantable medical devices cannot occur. The metals that are implanted into the human body have many requirements to meet. These include high corrosion resistance, long fatigue life, and biological compatibility to prevent adverse reactions.
The continued use of 316LVM stainless steel as the benchmark for medical implants can be attributed to its ability to provide a number of benefits to the surgeon and patient. Vacuum melting provides a very pure melt; controlled levels of inclusion are maintained during processing; and it has been shown to be biocompatible.
While selecting the appropriate grade of 316LVM is important for the medical device manufacturer, it is equally important to select a reliable source of 316LVM for all implant grades. This paper discusses why 316LVM will continue to be the best grade available and what makes a material suitable for use as an implant.
What is 316LVM Stainless Steel?
316LVM is a vacuum-melted, low-carbon austenitic stainless steel that was produced to meet the strict cleanliness and consistency requirements for medical implants.
The name 316LVM has the following components:
- 316 — Molybdenum-bearing stainless steel
- L — Low carbon (enhanced corrosion resistance)
- VIM/VIM-VAR — Vacuum induction melted, and/or Vacuum Arc remelted
- Medical Grade — Controlled Chemistry & Micro cleanliness
Vacuum melting has greatly reduced impurities, inclusions and gas content of this alloy so that it can be classified as an implant grade alloy with specifications from ASTM F138 and ISO 5832-1.
Why Implant-Grade Cleanliness Is Critical for Long-Term Patient Safety
Implantable metal materials are required to be stable within the human body, which contains a combination of salts, proteins, oxygen, etc., and complex chemistries. The presence of any contaminants, inclusions, or tramp elements in the steel used for implants can:
- initiate localized corrosion at points of inclusion
- weaken the local mechanical properties of the material
- induce an inflammatory response
- affects the longevity of the implant
As such, 316LVM is manufactured to minimize inclusion and tramp element content (contaminants) that would compromise structural integrity, long-term corrosion resistance and predictable performance in vivo.
Therefore, it is a reason why Surgeons, Device Manufacturers and Regulatory Authorities have confidence in using 316LVM.
Vacuum Melted 316LVM Stainless Steel: The Difference That Protects Implants
What truly differentiates 316LVM from conventional stainless steel is the vacuum melting process.
Vacuum Induction Melting (VIM)
Molten steel is refined under vacuum to remove:
- dissolved gases
- nitrogen
- hydrogen
- volatile impurities
This enhances micro-cleanliness as well as reduces oxide inclusions.
Optional Secondary Remelting (VAR)
Some manufacturers also remelt using VAR to provide an additional level of homogenization.
Result?
- Ultra clean chemistry
- Uniform fine-grain microstructure
- Very low inclusion content, which is necessary for medical implants
Superior Corrosion Resistance in the Body
316LVM contains molybdenum, which enhances resistance to:
- pitting
- crevice corrosion
- chloride attack
Particularly important in physiological environments
The low carbon content (L-grade) prevents carbide precipitation, protecting corrosion resistance during forming and sterilization.
This stability is why 316LVM is trusted in:
- bone screws
- plates
- cardiovascular devices
- surgical instruments
- neuro & spinal implants
Biocompatibility — A Proven Track Record
The most important feature is biocompatibility.
316LVM has:
- over 40 years of safe clinical experience
- regulatory approval
- a history of how 316LVM responds biologically
316LVM does not leach dangerous amounts of harmful substances and is generally well-tolerated by all patients, making it an ideal choice for long-term implantation.
Inclusion Control in 316LVM: A Key Factor in Fatigue Life & Implant Reliability
Controlling nonmetallic inclusions in 316LVM provides:
- fatigue performance that is reproducible
- less chance for micro defects to form
- predictability when machining or shaping 316LVM
- greater potential for good surface finishes
For medical devices (implants) that are subject to cyclic loading (e.g., orthopedic implants), the reproducibility of fatigue life is vital to ensure the reliability and safety of the patient.
Why 316LVM Remains the Benchmark
Although there are now a variety of advanced biomaterials, including Titanium and Cobalt-Chromium that have become very popular, 316LVM is still at the top of its class when it comes to:
- Maturity of Manufacturing
- Familiarity with Regulatory Agencies
- Mechanical Properties
- Cost Performance Ratio
- Global Availability
The reason for this is its ability to combine five key characteristics that make it one of the most versatile implant-grade materials:
- Strength
- Ductility
- Corrosion Resistance
- Purity
- Biocompatibility
Because of these five characteristics, 316LVM has many applications that include but are not limited to:
- Orthopedic Fixation Devices (e.g. Screws, Plates, Rods)
- Cardiovascular Implants (e.g. Valves, Stents)
- Dental Components (e.g. Crowns, Bridges)
- Guidewires & Springs
- Surgical Tools
- Neuro-Spinal Devices
Additionally, due to its formability, 316LVM can be made into wire, bar, strip or precision-machined parts.
At Venus Wires, the company manufactures implant-grade 316LVM stainless steel with extremely tight control over all chemical compositions, inclusions and surface finish, making the company's product compliant with international standards including ASTM F138 and ISO 5832-1. The company has developed advanced melting processes and has been providing expert metallurgy services for many decades, and provides support to medical device companies looking for reliable, high-quality materials that provide consistent performance for critical implant devices.
With an ever increasing regulatory environment and the need for higher performing implants, 316LVM stainless steel is still the world’s number one choice for implantable devices. The material offers a perfect balance of pureness, corrosion-resistant properties, mechanical reliability and biocompatibility that sets the bar for all other implant materials.
When coupled with controlled manufacturing and a steady supply chain, 316LVM can be used as a base for a patient's safe and successful use of an implantable device.
Also Read: Understanding Medical Grade Stainless Steel