Estudo da conformabilidade de alumínio, cobre e aço aisi 304 em temperatura criogênica

Abstract

Commercially pure aluminum and copper sheets and AISI 304 stainless steel were subjected to Olsen-type drawing and uniaxial tensile tests for anisotropy analysis at room temperature (25°C) and cryogenic temperature (-170°C). The numerical increase of approximately 9.6% in the results of the drawing indices in the cryogenic condition for aluminum and 14.7% for copper does not manifest itself in the same way in the 304 stainless steel, as evidenced by the visioplastic tests. In the case of aluminum, the normal anisotropy coefficients (Lankford index) exhibit significantly higher values at low temperatures compared to room temperature in the orientations 0°, 45° and 90° in relation to the rolling direction. Furthermore, for aluminum, it is observed that the planar anisotropy coefficient (ΔR) is lower at room temperature (0.21) and higher in cryogenic conditions (0.72). This suggests that anisotropy is more pronounced at cryogenic temperatures and influences the metal's formability. Regarding copper, the calculation of the planar anisotropy coefficient (ΔR) at room temperature was -0.10 to -0.26 under cryogenic conditions, a variation of 61.5%, which can result in defects during manufacturing, such as earing under cryogenic conditions. Regarding the tensile tests for the analysis of the anisotropy of 304 stainless steel, it is noted that in different rolling directions, the yield stress reaches approximately 1400 N at room temperature. However, at cryogenic temperatures, an increase of approximately 56% in the applied load is observed at 0°, 52.7% at 45° and 48% at 90° in all rolling directions. Despite supporting higher loads, the specimens exhibit lower deformation, resulting in a value of ΔR = 0.08 at cryogenic condition, which is 8 times higher than at room temperature. This suggests a tendency for earing to form during cryogenic processing.