Formability Evaluation of Two Austenitic Stainless Steels

Abstract

In this work, a comparative study was performed with two austenitic stainless steels: one of the standard type AISI 304 (18% Cr / 8% Ni / 1,3% Mn / 0,07% Cu / 0,033% N, in weight) and other where nickel was partially replaced by manganese, nitrogen and copper (16,3% Cr / 1,5% Ni / 7,4% Mn / 2,9% Cu / 0,184% N, in weight). The aim was to reduce the cost of the final product preserving its good formability and corrosion resistance properties. In order to determine the degree of stability of the austenite, isothermal tensile tests were performed on samples of the two steels in the range of temperature from -25 to 70°C. The amount of α'′ martensite formed was measured with a ferrite detector. Microhardness tests showed that the hardness of both steels increase with the amount of induced martensite. Microstructural characterization of the deformed samples was performed by Optical Microscopy and Atomic Force Microscopy. The mechanical properties were studied by tension and formability tests (Erichsen and Swift). It was verified that the AISI 304 steel presents better formability (stretch formability) than the steel with partial substitution of Ni by Mn, Cu and N.