Physical properties of stainless steel, the main material of acupuncture needles
According to relevant sources, the main material of the needle body of the current acupuncture needles on the market is stainless steel. The main physical properties of this material are:
1. Carbon steel, ferritic and martensitic stainless steels are magnetic, and austenitic stainless steels are non-magnetic, but they will produce magnetism when they are cold-worked and hardened to form martensite transformation. Heat treatment can be used to eliminate this martensite. The tissue is restored to its non-magnetic properties.
2. The order of linear expansion coefficient is similar, austenitic stainless steel is higher and carbon steel is smaller.
3. Resistivity: Resistivity is in increasing order of carbon steel, ferritic, martensitic and austenitic stainless steel.
4. Density: The density of carbon steel is slightly higher than that of ferritic and martensitic stainless steel, and slightly lower than that of austenitic stainless steel.