Introduction
Medical stainless steel is a specialized type of stainless steel designed to meet the rigorous demands of medical applications. With superior corrosion resistance, biocompatibility, and mechanical properties, it is essential for ensuring the safety and longevity of medical implants and instruments. This article will explore 12 crucial facts about medical stainless steel, from its chemical composition requirements to its various applications, including its use in antibacterial applications. Understanding these facts is vital for anyone involved in the production, use, or selection of medical stainless steel products.
What Are the Differences Between Medical and Industrial Stainless Steel?
Compared to industrial stainless steel, medical stainless steel requires superior corrosion resistance within the human body to minimize metal ion leaching and avoid intergranular and stress corrosion that can lead to implant failure. Therefore, the chemical composition requirements for medical stainless steel are stricter.
What Are the Chemical Composition Requirements for Medical Stainless Steel?
Medical stainless steel, especially for implants, contains higher levels of alloying elements like Ni and Cr compared to ordinary stainless steel. Impurity elements like S and P are lower. The size of non-metallic inclusions in the steel must be smaller than 1.5 microns for fine inclusions and 10 microns for coarse inclusions, which is not specifically required for industrial stainless steel.
How Is Intergranular Corrosion Prevented in Medical Stainless Steel?
To prevent intergranular corrosion, medical stainless steel requires lower carbon content. Early standards set carbon content limits at 0.08% and 0.03%. With advancements in metallurgy and higher application requirements, recent standards (e.g., ASTM F138-03, ASTM F139-03, ISO 5832-1-2007, GB 4234-2003) mandate a carbon content not exceeding 0.03%.
How Is the Strength and Hardness of Medical Stainless Steel Enhanced?
Commonly used austenitic stainless steels like 316L or 317L have relatively low strength and hardness in their solution-treated state but can be enhanced through cold working. Surgical implants typically use cold-worked stainless steel (about 20% deformation) to meet high strength and hardness requirements. However, cold working increases sensitivity to stress corrosion and fatigue failure.
Why Is Medical Stainless Steel Widely Used?
Medical stainless steel is extensively used for its excellent biocompatibility, mechanical properties, corrosion resistance in body fluids, and formability. It is commonly used to make various artificial joints and internal fixation devices such as artificial hip joints, knee joints, shoulder joints, elbow joints, wrist joints, ankle joints, finger joints, osteotomy connectors, compression plates, bone screws, spinal nails, bone traction wires, and artificial vertebral bodies.
What Are the Applications of Medical Stainless Steel in Dentistry?
In dentistry, medical stainless steel is used for dentures, orthodontics, dental implants, and auxiliary devices like crowns, bridges, fixed supports, clasps, base plates, inlays, orthodontic arch wires, prosthetics, and maxillofacial defect repairs.
How Is the Demand for Medical Stainless Steel in China?
In recent years, the demand for high-quality and affordable medical stainless steel wire, rods, orthopedic plates, screws, and other semi-finished products in China’s medical device industry has significantly increased, exceeding hundreds of tons annually. Currently, China has only two standards for medical implant stainless steel, GB 4234 (equivalent to ISO 5832-1 and ASTM F138) and YY 0605-19-2007 (equivalent to ISO 5832-9 and ASTM F1586). The standardization work for medical stainless steel in China lags behind the United States, which has revised six types of surgical implant stainless steels.
What Is Antibacterial Stainless Steel?
Antibacterial stainless steel is a new type of stainless steel that incorporates a certain amount of antibacterial elements (such as copper and silver) to maintain stable processing properties and good antibacterial performance after antibacterial treatment.
What Are the Classifications of Antibacterial Stainless Steel?
Antibacterial stainless steel can be classified according to different methods, as shown in the following figure.
- By Manufacturing Method
Surface Coating Antibacterial Stainless Steel
Composite Antibacterial Stainless Steel
Surface Modified Antibacterial Stainless Steel
Overall Element-Added Antibacterial Stainless Steel
- By Added Antibacterial Element
Copper-Containing Antibacterial Stainless Steel
Silver-Containing Antibacterial Stainless Steel
Zinc-Containing Antibacterial Stainless Steel
Rare Earth Element-Containing Antibacterial Stainless Steel
- By Type of Added Antibacterial Element
Ferritic Antibacterial Stainless Steel
Austenitic Antibacterial Stainless Steel
Which Metal Ions Are Safe and Antibacterial for Humans?
Most metal ions have strong bactericidal properties. The antibacterial performance of metal atoms or their ions that are safe for humans and animals is ranked as follows: Ag+ > Co2+ ≥ Ni2+ ≥ Al3+ ≥ Zn2+ ≥ Cu2+ = Fe3+ > Mn2+ ≥ Sn2+ ≥ Ba2+ ≥ Mg2+ ≥ Ca2+.
What Is the Antibacterial Mechanism of Antibacterial Stainless Steel?
Different antibacterial elements have different antibacterial effects. When in contact with bacteria, metal ions like Cu, Ag, Zn, and newly studied rare earth metals enter bacterial cells, combining with enzymes and rendering the bacteria inactive, thus achieving good antibacterial effects.
What Are the Applications of Antibacterial Stainless Steel?
- Manufacturing medical devices: Meeting sterile requirements, reducing frequent sterilization, and ensuring sterility under normal conditions.
- Medical facility components: Used in bathroom fixtures, dining utensils, work surfaces, and various facilities in patient areas like door handles, handrails, and food carts to prevent bacterial transmission and cross-infection.
- Pharmaceutical machinery and containers: Ensuring a clean environment during drug production.
- Food processing, storage, and transportation equipment: Ensuring sterility and preventing foodborne illnesses.
Conclusion
Discover essential facts about medical and antibacterial stainless steel, including their chemical composition, corrosion resistance, and diverse applications in healthcare. Learn how these materials ensure safety and effectiveness in medical devices, implants, and instruments, making them vital for the healthcare industry and improving patient outcomes.