Nickel-free high-nitrogen austenitic stainless steel

The latest developed product "Ergste9.9007CN" in the high-nitrogen stainless steel series by ZAPP (Germany).

The steel type has aimed to exclude nickel from the development stage to enhance biocompatibility. High-purity raw materials have been carefully selected for melting. As a result, the nickel content is below 0.05%, and the level of micro-slag inclusion is very low. Additionally, pressurized electro-slag remelting (P-ESR) is performed for re-melting. Traditionally, the chemical composition of nickel-free high-nitrogen stainless steel contained high levels of 1% nitrogen and 20% manganese. Since the solubility of nitrogen is limited, a higher nitrogen content tends to form chromium nitride precipitates. Manganese must retain nitrogen in the solid solution, which also compromises corrosion resistance. Furthermore, machinability becomes more difficult as the nitrogen content increases. The solution to these issues was to replace nitrogen with carbon. In traditional metallurgy, a high carbon content in conventional austenite is disadvantageous. However, when used in combination with nitrogen and carbon, it resolves the problems caused by excessive nitrogen usage. At ZAPP, careful and thorough analysis was conducted in the development of this steel type to achieve a balanced composition design and realize its commercialization.

stainless