Fourth

When stainless steels were first produced in the early 1900s they were recognized mainly for their corrosion resistance. Upon continued development, different s/s alloys were made that exhibited unique and import  properties, for example, alloys that could maintain mechanical properties in high temperatures, in several thousands of degrees, such as turbine blades that would not corrode and yet function. Similar alloys made it possible to build containment vessels for nuclear reactions.

In a nut-shell this is what is wrong with choosing 316LVM. The grade was not selected based on properties needed for body piercing, but for medical orthopedic implants, such as bone fixation plates and screws, and joint replacements. The obvious conclusion is the choice came first followed by attempts to justify it.

Beddoes and Parr describe a proper procedure used to select stainless steels.

In Section 1.6, Selection of Stainless Steels, Introduction to Stainless Steels, they write

We suggest that you write down in order of priority, on the left hand side of a page, those particular properties sought. The list probably begins with corrosion resistance in a defined environment, moves into particular mechanical properties, and fades out with magnetic hysteresis. Give each property a number that is in rough proportion to its importance. Then, to the right of this list, enter the classes of stainless steel that will accommodate each requirement. (Intro.:1999:19)

Given the basic requirements of a stainless steel (i.e. that it should be corrosion resistant under particular circumstance of environment and stress, the name of the game is simply to make those adjustments [in the formula] so that the best possible combination of properties is achieved. (Intro.:199915)

The APP selection and promotion of F138 certified 316LVM will not bear scrutiny and must be rejected based on research and historical experience.

Properties of Stainless Steels

Chemical Properties;

As far as we are concerned, this pertains almost exclusively to corrosion resistance.... Unfortunately, however, while engineering design may be substantially based upon measured physical and mechanical properties, no chemical equation - or simple corrosion test-offers the same level of predictability. Hence, while knowledge of corrosion principles is vitally important to the sensible selection and application of stainless steels, we must rely heavily on recorded experience. (Into.1999:14)

For the purpose of selecting steels for body piercing, this principle demonstrates that the millions of safe piercings using 316L is not top be ignored.

...chemical analysis ... is routine ... careful and sophisticated because performance depends upon ... the correct chemical composition on which the initial choice of steel ... depends. (1999:68)

In corrosion testing, long-term tests provide a continuously updated arsenal of invaluable information (maintained by several sources) about corrosion in a variety of atmospheric conditions and soils. If the circumstances of alloy and environment have not been explored, there is no option but to take a sample and try to reproduce the anticipated environmental conditions, or more commonly to apply a test which is known to be indicative of performance. (1999:70)

...nothing can substitute for an encyclopedic knowledge of past experiences(1999:70)

Physical Properties (1999:15)

Physical properties are, of course important, and we do refer to them. But these properties are fairly constant within each stainless steel class. ... They know too, that [the the physical characteristics, some of which are listed below of a given alloy formula] ... will not vary significantly from one shipment to the next. (1999:68)

specific gravity - will not vary significantly from one shipment to the next
electrical conductivity - will not vary significantly from one shipment to the next
magnetic susceptibility - will not vary significantly from one shipment to the next
thermal conductivity - will not vary significantly from one shipment to the next

Mechanical Properties

Such consistency is not necessarily the case with mechanical properties ...these may vary from heat to heat and are considerably affected by subsequent processing (1999:68)

We are provided additional information here, that the mechanical properties also depend on what is done during the fabrication of the finished item. It is likely that ASTM has looked at standards to certify finished products and equally unlikely that local body jewelry companies certify the finished products they fabricate.

the strength of our materials:

ultimate tensile strength - when the material breaks in tension
elastic limit: the strength that can be sustained before the material yields and will not return to     its original  shape
toughness: involves ductility and strength and is a measure of the ability of a material to absorb energy. In more practical terms, toughness pertains to resistance of a material to fracture when stress concentrates - as it inevitable does - at a notch, a crack, perhaps a brittle constituent at a grain boundary.

...wet or moist and contaminated. ... unprotected plain-carbon steels corrode, as do the low-alloy steels: but the stainless steels generally do not because their chromium content causes the formation of that important, protective, passive layer. They do not discolor in a normal atmospheric environment, nor are they attacked by dilute nitric acid... They were said, therefore, not to stain and so became known as stainless steels. (Introduction, 1999:1)

One of the errors APP and others perpetuate is failing to acknowledge that the environment for body piercing jewelry is not the same as for orthopedic implants. The specific properties of a stainless steel alloy to survive in a bio-active, mechanically and physically stressed environment are far different than the properties required for a belly ring that is outside and separate from the body in an air-exposed dry atmosphere. That makes all the difference in the world.

It is the same with 316LVM, a patented product with a reduced ferrite content and decrease in impurities important for orthopedic implants, such as joint implants, and applications under stress and mechanical wearing. In a load-bearing implant of two mating surfaces rub against each other with up to 150% of body weight, cyclically loading and unloading. This rubbing under pressure, starting and stopping, causes atoms to separate from the implant surface and become free-floating, as it were, between the two surfaces which increases exponentially, ultimately resulting in the loss of the implant to the patient. Currently this is seen as inevitable. A s/s implant is found to last longer when a more homogenous, purer form of material is used freer from impurities, and what are called ferrites. 316LVM is formulated to address these problems.

The developments in s/s relate not only to the actual chemical composition...  [but] heat treatments, fabrication techniques, and the steelmaking process...[affect] ... toughness [even at] .. very low temperatures only slightly above absolute zero. All have specific features of resistance to corrosion, although ... none is universally applicable. (Introduction 1999:2)

There are about two hundred commercially available stainless steel compositions, each with properties that are influenced by heat treatment and the manner of fabrication .. [there are many factors] that should influence our selection {when specifying the qualities necessary for a particular application or use.]. (Intro 1999:7)