Effect of Carbon on the Cold-worked State and Annealing Behavior of Two 18wt%Cr–8wt%Ni Austenitic Stainless Steels

抄録

The influence of carbon on the work hardening, formation and reversion of deformation induced martensite and on the recrystallization of two austenitic stainless steels 18%Cr–8%Ni type were studied with the help of different microstructural analysis techniques. Two steels were selected: the first an AISI 304L with low carbon (%C=0.021) content and the second an AISI 304 with higher carbon (%C=0.065) content. Both steels were heat treated to obtain two different initial conditions: one with the carbon completely in solid solution (after a solution annealing treatment at 1100°C) and the other with practically all the carbon in the precipitated form, as (Cr, Fe)₂₃C₆ (after a precipitation treatment at 750°C). The material having higher carbon content, both in solid solution and precipitated, presented in both cases higher strain hardening, smaller tendency to form strain induced martensite and higher resistance to recrystallization. Carbon in solid solution, as compared to the precipitated condition, led to a material with a higher tendency to strain hardening, less susceptibility to martensite formation and more resistance to recrystallization. Nucleation of recrystallization preferably occurred in the vicinity of grain boundaries. Based on the results of the kinetics of recrystallization and intergranular corrosion tests it was concluded that the usually recommended annealing temperatures (1000 to 1120°C) are sometimes unnecessarily high.