The 316L vs. 316LVM Debate!

by Ron Fante, The Body Wire Co.

I understand that the debate on 316L & 316LVM continues. I'm not quite sure if I can clear up all the issues, but I'll tell you what I know, hopefully it will help resolve a few misconceptions.

First of all it's important to understand the relationship between ASTM-F138, 316LVM and 316L with respect to microcleanliness.  The most common versions of 316L and 316LVM generally meet the requirements of ASTM-A-580, ASTM-A-276, ASTM-A-479 and QQS763. They also typically meet the Intergranular Corrosion Resistance requirements of ASTM-A-262 Practice E, if annealed correctly. However they do not meet the requirements of ASTM-F-138. This specification is unique in that it has a modified chemistry and microcleanliness requirements (inclusion limitations).  To meet this requirement, additional processing is performed at the mill.  Often the preferred process is vacuum melting (VM).  However, there are different types of re-melting processes used to achieve the microcleanliness requirements of ASTM-F-138, such as Electro Slag Re-melt (ESR), Vacuum Arc Re-Melt (VAR) and Vacuum Induction Melting (VIM).

Even though microcleanliness plays a very important role in qualifying a material as Implant Quality, the additional Nickel plays a very important role also.  The nickel has been increased to 13.00/15.50% to insure that the material will not become magnetic during cold working in the manufacturing process.  It also offers additional corrosion resistance.  Standard 316L or 316LVM has a lower nickel content (10.00/14.00) and is usually at the low end of this range, consequently the material can become magnetic after severe cold working.

I often hear comments about the Chromium oxide layer on the surface of 316LVM F-138. This is true, but I feel clarification is needed. All stainless steel has a Chromium oxide layer on the surface. This is one of the primary reasons stainless steel resists corrosion. The combination of Chromium, Nickel and Molybdenum allows for different degrees of corrosion resistance. In the case of 316L, or 316LVM more Chromium and Nickel is added for this reason. Molybdenum is also added to help the Chromium and Nickel do their job.

If you have any questions or concerns, please call Ron Fante 714 899 9031 or email at ron@bodywireco.com