The ASTM F139 standard was created to unify the production and quality control of wrought stainless steel sheets and strips employed in surgical implantations. It is a chemically identical alloy, UNS S31673, that is manufactured with much stricter guidelines to ensure that it contains a low level of carbon, few inclusions, and is highly resistant to corrosion compared to Type 316 stainless steel. It is composed of 18 percent chromium, 14 percent nickel, and 2.5 percent molybdenum, which offers good pitting and crevice-corrosion protection in chloride and fluid body environments as found in human body fluids. The standard regulates chemical composition, mechanical properties, melting practice, surface condition, and testing processes in order to provide biocompatibility. It is utilized in the manufacture of orthopedic components, surgical clips, cardiovascular components, and dental apparatuses in which flexibility, surface finish, and cleanliness are vital.
ASTM F139 Standard Specification for Wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless Steel Sheet and Strip for Surgical Implants (UNS S31673)
What is ASTM F139?
What is the Scope of ASTM F139?
ASTM F139 has established specifications and performance criteria regarding wrought 18Cr-14Ni-2.5Mo stainless steel sheet and strip (UNS S31673) to be used as surgical implants. The standard guarantees the use of such materials of high corrosion resistance, controlled microstructure, and mechanical strength required in biological environments. It is applicable to flat-rolled products that are used in implantable medical devices, surgical components, and biomedical products that need the tissue to be compatible and stable over a long period.
Materials Commonly Tested with ASTM F139
ASTM F139 is mostly applied to cold-rolled and annealed stainless steel sheets and strips that are utilized in the production of implantable components, including surgical plates, clips, and flexible parts that need to be formed precisely and biocompatibly.
Applications of ASTM F139 in Industry
Medical device manufacturers have used the specification to manufacture orthopedic fixation plates, stents, prosthetic supports, and dental components in large numbers. It is corrosion-resistant and has high mechanical reliability, thus it can be permanently or temporarily implanted.
ASTM F139 Equipment and Sample Preparation
| Specimen sampling and dimensions | Sampling shall be made from finished sheet or strip products that are 0.2 to 3 mm thick, depending upon the intended implant design. Each lot shall represent a uniform processing history. |
| Surface preparation | The surface of the test specimen must be smooth, clean, and free of scale, pits, or foreign material. Final finishing may include polishing and passivation using nitric or citric acid solutions. |
| Melting and processing | The alloy shall be made by an electric furnace process followed by vacuum arc or electroslag remelting to refine the inclusions and produce a homogeneous alloy in sheet and strip form. |
ASTM F139 Testing Procedure and Requirements
| Chemical composition analysis | The alloy shall contain 17.0–19.0 % Cr, 13.0–15.0 % Ni, 2.25–3.00 % Mo, with maximum limits of 0.03 % C, 0.025 % P, and 0.010 % S, verified by spectrochemical or wet chemical analysis. |
| Mechanical property verification | Tensile strength to be minimum 860 MPa, yield strength at least 520 MPa, and elongation minimum 40 %. Hardness values shall comply with the limits prescribed for the annealed condition. |
| Corrosion and microstructure evaluation | The microstructure shall be fully austenitic with no carbide precipitation. Corrosion resistance is checked by immersion tests such as those described in ASTM F745 or equivalent. |
ASTM F139 Result Analysis and Interpretation
ASTM F139 conformance is manifested when all chemical, mechanical, and corrosion-resistance requirements are met. A compliant product has a homogenous microstructure, consistent mechanical strength, and corrosion resistance to body fluids. Any non-conformity to the compositional or mechanical boundaries means non-conformity, and the lot cannot be used as a surgical implant.
ASTM F139 Related Articles
Other articles pertaining to the same are ASTM F138, which addresses bar and wire forms of the identical alloy used in surgical implants; ASTM F899, which gives chemical composition requirements of surgical stainless steels; ASTM F745, which addresses corrosion testing of implant alloys, and ASTM F1537, which addresses cobalt-chromium-molybdenum alloys used in orthopedic applications.
Safety and Best Practices in ASTM F139
To maintain biocompatibility, manufacturing should have contamination-free environments, controlled melting, and adequate passivation. They should be tested in a calibrated laboratory, and the handling of the materials should not cause mechanical or chemical damage to the surface.
Importance of ASTM F139
ASTM F139 is a standard that can be used to evaluate the quality, safety, and consistency of sheet and strip stainless steel that is utilized in surgical implants. It guarantees that the materials present reliable strength, corrosion resistance, and biological safety- aspects that are vital to the health of patients and the ultimate success of implantable medical devices.
Updated on September 17, 2026
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