by Ron Fante, The Body Wire Co.
www.bodywireco.com

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, 316LVM, 316L and Cleanliness/Inclusions. 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 (much different then standard 316LVM or 316L) and more stringed cleanliness requirements. But most importantly, it has inclusion limitations. Inclusions can be defined many different ways, but typically they are internal in the form of stringers. Inclusions are not limited to the internal structure. They can be apparent on the surface also. Any surface imperfection can be a detriment to the materials end use. Surface imperfections can take the form of stringers, pitting and even scratches. The vacuum melting process can alleviate stringers (type of inclusion) and impurities in the material such as sulfur, phosphorous, and unwanted gases (Note: There are other types of remelting processes besides vacuum melting (VM) used to achieve the cleanliness/inclusion requirements of F-138.). Pitting, scratches and other surface imperfections must be eliminated by surface removal and good polishing technique.

Most experts recommend that material used for implants must comply with ASTM-F-138 even though standard 316L was used for many years before they switched to Titanium and 316LVM (F-138) material. This is apparent due to the fact that the second largest melting mill of stainless steels in the country (Crucible Steel), lists "surgical implants" as a typical application on their standard 316L data sheet. What does this mean? I believe the answer to this question is understanding "Nonmetallic Inclusions" and how they effect the material. These inclusions are imperfections in the material caused by nonmetallic elements which have a tendency to segregate, forming a stringer. These imperfections can harbor bacteria. Therefore, surface preparation during the jewelry manufacturing process becomes critical. The surface must be relatively free of inclusions. It is true that the Vacuum Melt (VM) process reduces nonmetallic inclusions, but F-138 is not necessary to accomplish this. The F-138 specification is considered implant quality primarily do to the increase in nickel content (13.00/15.50) which is added to insure that the material will not become magnetic during cold working in the manufacturing process. Standard 316L and 316LVM has a lower nickel content (10.00/14.00) and is generally at the low end.

It's important for an implant to be nonmagnetic for obvious reasons. Body Piercing is not an implant. Therefore, standard 316LVM is more than adequate for this application. As far as standard 316L is concerned, this material can also be used if proper surface preparation is applied and followed by magnified surface inspection. I cannot over emphasize this point. It is absolutely critical that the surface is polished adequately so it is free of imperfections caused by inclusions or otherwise. This is most probably why the APP recommends 316LVM material. I can only guess why they also recommend ASTM- F-138. It may be because they don't understand the relationship between 316LVM and F-138. I have been told that there are some States that have mandated F-138 for body piercing. If this is true, I feel this is a precautionary decision made for the same reasons or because they are not certain as to the extent the material is exposed to blood and tissue. If a jewelry manufacturer has any doubts as to their ability to prepare the surface of their product adequately, then upgrade to 316LVM, or 316LVM to the F-138.

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.

In closing I would like to add that I believe some of the problems in the industry exist do to poor processing of the material. I know of many in the industry that heat the material after forming in an effort to make it softer. This will most likely ruin the properties the material was designed to develop. A certified heat treater should always be used when ever you desire a softer material. Atmosphere, Time and Temperature is critical when annealing (softening) this type of material. Many things can be effected adversely if improperly annealed, such as surface imperfections (pitting), inadequate corrosion resistance and grain structure. These are important factors that will effect the end user adversely.

If you have any questions or concerns, please call Ron Fante 714 899 9031