5 Minutes To Introduce You to What is Medical Stainless Steel
Compared with industrial stainless steel, medical stainless steel is required to maintain excellent corrosion resistance in the human body to reduce the dissolution of metal ions, to avoid intergranular corrosion, stress corrosion and other local corrosion phenomena, to prevent the failure of the implanted device fracture, to ensure the safety of implanted devices, so its chemical composition requirements are relatively more stringent.
Medical stainless steel, especially implantable stainless steel, in which the content of alloying elements such as Ni and Cr are higher than ordinary stainless steel (usually reaching the upper limit of ordinary stainless steel requirements), S and P and other impurity elements to be lower than ordinary stainless steel, and specify the size of non-metallic inclusions in steel to be less than 115 (fine) and 1 (coarse), and ordinary industrial stainless steel standards and inclusions are not Special requirements.
In order to avoid intergranular corrosion of medical stainless steel, but also requires a lower C content, while the early provisions of the C content is not higher than 0108% and 0103% two levels (mass fraction). With the progress of metallurgical technology and application requirements, in recent years, the revision of domestic and international standards for medical stainless steel, all require the C content of steel is not higher than 0103% (such as ASTMF138-03, ASTMF139-03, ISO5832-1-2007, GB4234-2003).
Medical stainless steel commonly used in 316L or 317L austenitic stainless steel in the solid solution state of the strength and hardness are low, but can be deformed by cold working to improve its strength and hardness. Therefore, the clinical use of surgical implant stainless steel is usually in the cold working state (cold working deformation of about 20%) to meet the requirements of implantable devices of high strength and high hardness, but the cold working state increases the sensitivity of medical stainless steel stress corrosion and corrosion fatigue damage.
Medical stainless steel has become a widely used clinical medical implant material and medical tool material because of its good biocompatibility, good mechanical properties, excellent resistance to corrosion of body fluids, and good processing and forming properties. Medical stainless steel is widely used to make a variety of artificial joints and fracture internal fixation devices, such as a variety of artificial hip, knee, shoulder, elbow, wrist, ankle and finger joints, various sizes of osteotomy connector, pressurized plate, goose head bone screws, spinal nails, bone traction wire, artificial vertebrae, as well as cranial plate, artificial vertebrae, etc..Commonly used surgical equipment is 316 stainless steel
In recent years, China’s medical device industry on the quality and low cost of medical stainless steel wire, bar, orthopedic special plates, screws and other semi-finished products, the demand has increased significantly, more than a few hundred tons per year. At present, there are only two domestic medical implant stainless steel standards, namely GB4234 (basically equivalent to ISO5832-1 and ASTMF138) and YY060519-2007 (equivalent to IS05832-9, corresponding to ASTMF1586), the standardization of medical stainless steel work is far behind the United States (its current revision of a total of six kinds of surgical implant stainless steel). Therefore, the new medical stainless steel standard revision work is also an important part of the future research and development of medical stainless steel in China.