AFFORDABLE STAINLESS STEEL

316LVM Stainless Steel

316LVM Stainless Steel is an electro-slag remelted (ESR) or vacuum arc remelted (VAR). The implant version (ASTM-F138) is a low carbon, high nickel and molybdenum version of 316L Stainless Steel. The secondary premium melting improves micro-cleanliness which is imperative for implant applications. The chemistry modifications are designed to maximize the corrosion resistance of this alloy and the additional Nickel alleviates the possibility of the material becoming magnetic even after severe cold working.

A commercial grade of 316LVM Stainless Steel is also available. Its chemical composition differs from the implantable version. It is offered with the same chemical composition as standard 316L (ASTM-A276), but it has been either electro-slag remelted (ESR) or vacuum arc remelted (VAR).

Standard Industry Specifications

• UNS S31673
• ASTM F138 (Bar) , ASTMF139 (Sheet – Plate)
• ASTM-A276, ASTM-F899
• ISO 5832-1 Composition D
• Common Trade Names
• BioDur® 316LS
• 316LVM ASTM-A276 ASTM-F899
• 316LVM Implant Grade ASTM-F138 Common Applications
• Fracture Fixation Devices
• Bone Plates
• Screws
• Intramedullary Nails
• Surgical Implant Devices
• Surgical Instruments

TYPE ANALYSIS

Single figures are nominal except where noted.

0.03%

0.025%

0.75%

13.00 to 15.00%

0.50%

Balance

Pitting Resistance Equivalent* = 26.00 min.

NOTE: Pitting Resistance Equivalent (PRE) = 3.3 x Mo + Cr

General Information

Description

This Stainless Steel is an electro-slag remelted (ESR) or vacuum arc remelted (VAR), low carbon, high nickel and molybdenum version of 316 stainless. The secondary premium melting step (ESR or VAR) imparts improved cleanliness. The chemistry modifications are designed to maximize the corrosion resistance of this alloy and provide a ferrite free microstructure. The alloy is nonmagnetic even after severe cold forming operations.

Applications

This material has found application in fracture fixation devices such as bone plates, screws, and intramedullary nails. This alloy has been used as machining and forging stock for producing surgical implant devices. The alloy has also been used in surgical instruments where high hardness is not a requirement.

Corrosion Resistance

This alloy is balanced with higher chromium, nickel and molybdenum than standard Type 316L stainless, thus increasing its resistance to pitting corrosion. This increased resistance to pitting is illustrated by a Pitting Resistance Equivalent (PRE) of greater than 26 as opposed to a PRE of 23 for standard Type 316L stainless. This chemistry balance, combined with the exceptional cleanliness from the VAR remelt practice and absence of ferrite, makes it an excellent candidate for orthopedic applications.

Important Note:

The following 4-level rating scale is intended for comparative purposes only. Corrosion testing is recommended; factors which affect corrosion resistance include temperature, concentration, pH, impurities, aeration, velocity, crevices, deposits, metallurgical condition, stress, surface finish and dissimilar metal contact.

Good

Moderate

Moderate

Moderate

Properties

Physical Properties

Specific Gravity

7.95

Density

0.2870	lb/in³

Mean Specific Heat

32 to 212°F    0.1200Btu/lb/°F

Mean CTE

32 to 1200°F    10.3    

x 10-6 in/in/°F

Electrical Resistivity

70°F	445.0	ohm-cir-mil/ft

Typical Mechanical Properties

Supplied in the annealed or cold worked condition. Mechanical properties can be tailored to specific applications by changing the cold work percentage. In general, the acceptable property ranges are dependent on bar size due to varying penetration of cold work.

Heat Treatment

Annealing

Annealing is accomplished by heating in the range of 1800/2050°F (982/1121°C). Typically, the alloy is annealed at the lower end of this range to preserve the fine grain size that is required for medical applications.

Hardening

This alloy cannot be hardened by heat treatment. It must be hardened by cold working.

Workability

Hot Working

This Stainless Steel can be readily forged, upset, and hot headed. To forge, heat uniformly to 2100/2300°F (1149/1260°C). Forgings may be air cooled. Best corrosion resistance is obtained if the forgings are given a subsequent anneal followed by a rapid quench.

Cold Working

It can be deep drawn, stamped, headed and upset without difficulty.

Machinability

The intentional reduction of sulfur and the cleanliness due to the VAR premium melting practice, and the typically highly cold worked structure make machining more difficult than standard Type 316L stainless.

Additional Machinability Notes

When using carbide tools, surface speed feet/minute (SFPM) can be increased between 2 and 3 times over the high-speed suggestions. Feeds can be increased between 50 and 100%.

Figures used for all metal removal operations covered are average. On certain work, the nature of the part may require adjustment of speeds and feeds. Each job has to be developed for best production results with optimum tool life. Speeds or feeds should be increased or decreased in small steps.

Weldability

Weldability It can be satisfactorily welded by the conventional automatic and manual electric-arc techniques. The low carbon content reduces the susceptibility to carbide precipitation in the heat affected zone; however, when optimum corrosion resistance is required, a post weld anneal is always considered good practice. Filler metal should be the same alloy as the parent. Because this alloy is balanced to have zero ferrite potential, it is more susceptible to weld hot cracking than standard Type 316L stainless. This effect may be minimized by keeping heat inputs, base metal dilution, and joint restraint to a minimum.