Due to the significant differences between medical stainless steel pipes and stainless steel in other fields, it is necessary to maintain stable and good corrosion resistance (including resistance to intergranular corrosion, stress corrosion, and other local corrosion) to prevent the rapid failure of implanted medical instruments, reduce the dissolution of harmful metal ions, and ensure the safety and reliability of clinical applications of stainless steel implant devices. Therefore, medical stainless steel pipes with good corrosion resistance are commonly used as implant materials for medical stainless steel. Currently, austenitic stainless steel materials with a stable austenitic structure system represented by 316L and 317L have been widely used clinically.
In fact, usually more than 10% nickel is added to medical grade stainless steel tubing, which is a loss compared to other structural materials currently used in clinical practice. Therefore, developing new medical stainless steel pipes and improving the performance of medical stainless steel is very important. Fortunately, a series of new medical stainless steel materials have been developed, such as high-nitrogen, nickel-free austenitic stainless steel, antibacterial stainless steel, and anti-ISR (in-stent restenosis) stainless steel for cardiovascular stents. The high-nitrogen, nickel-free austenitic stainless steel has excellent performance. As nickel in stainless steel may be harmful to the human body, developing low-nickel and nickel-free medical austenitic stainless steel is the main development direction of medical stainless steel in the world. Nitrogen can strongly stabilize the austenitic structure in stainless steel. Therefore, using (nitrogen-manganese) instead of nickel in stainless steel can stabilize the austenitic structure and significantly improve the mechanical performance and corrosion resistance of medical stainless steel pipes. Medical stainless steel pipes are also widely used in the market.
Cardiovascular interventions have treated many patients with coronary heart disease caused by coronary artery stenosis. However, clinical problems of ISR are prone to occur after stent implantation, especially within 3–6 months after stent implantation, with an incidence rate of up to 20%-30%. Scientific research has found that trace amounts of copper have many benefits for the human cardiovascular system. If trace amounts of copper can be continuously released in situ, it can inhibit restenosis within the stent from a material perspective.
Therefore, based on the widely used 316L stainless steel for cardiovascular stents, research institutions have developed copper-containing stainless steel for cardiovascular stents, so that medical stainless steel tubing can continuously release trace amounts of copper in situ after implantation, making the stent not only provide mechanical support but also inhibit ISR. The results show that medical stainless steel pipes can significantly reduce the adhesion of platelets on their surface, thereby reducing the tendency of thrombosis formation. Therefore, it can be seen that copper-containing stainless steel should have medical functions to inhibit the occurrence of ISR, so anti-ISR stainless steel used to manufacture cardiovascular stents should have great prospects.