4. Dynamic Characterization of Nitronic 30, 40 and 50 Series Stainless Steels by Numerical Analysis

Nitronic® stainless steels are austenitic, high-strength, corrosion-resistant products that provide higher-performance alternatives to many conventional 300 and 400 Series stainless steels. They provide excellent mechanical properties at sub-zero and elevated temperatures, impact resistance at low temperatures and, superb resistance to high- temperature oxidation while they retain good weldability and fabricability. The microstructure of Nitronic^® 30, 40 and 50 series of 25 and 35 % cold worked, thermally aged at 750 C for 8 h, and annealed coupons was characterized by metallography, X-ray diffraction (XRD) and scanning electron microscopy. The coupons etching of each series needed specific attention and it resulted in an improved procedure. Nitronic® 50 steels remain non-magnetic even after extensive cold work. Nitronic 50 metallographic analysis showed the existence of cementite and enlarged grain boundaries after thermal ageing. The austenite, martensite and ε phases were recognized by XRD. The dynamic behavior of these alloys was studied by modeling and simulation using the commercial software ANSYS/AUTODYN and was compared to simulation results of projectile made of 4340 steel on known materials models. The correlation of the microstructure to the alloy properties and the dynamic behavior of these alloys will be presented in detail.