Metallurgical Studies of Austenitic Stainless Steel 304 under Warm Deep Drawing

Austenitic stainless steel 304 was deep drawn with different blank diameters under warm conditions using 20 t hydraulic press. A number of deep drawing experiments both at room temperature and at 150 °C were conducted to study the metallography. Also, tensile test experiments were conducted on a universal testing machine up to 700 °C and the broken specimens were used to study the fractography of the material using scanning electron microscopy in various regions. The microstructure changes were observed at limiting draw ratio (LDR) when the cup is drawn at different temperatures. In austenitic stainless steel, martensite formation takes place that is not only affected by temperature, but also influenced by the rate at which the material is deformed. In austenitic stainless steel 304, dynamic strain regime appears above 300 °C and it decreases the formability of material due to brittle fracture as studied in its fractography. From the metallographic studies, the maximum LDR of the material is observed at 150 °C before dynamic strain regime. It is also observed that at 150 °C, grains are coarse in the drawn cups at LDR.