Method for batch annealing of austenitic stainless steels

Abstract

Methods are provided for annealing coils of austenitic stainless steels through the use of a batch annealing process. The preferred methods involved selecting compositions of austenitic stainless steel alloys having a sufficiently low weight percentage of carbon so that annealing of the austenitic stainless steel occurs without intergranular carbide precipitation at a temperature of less than about 1700.degree. F., which is well below the normal annealing temperature for austenitic stainless steels. The lower annealing temperatures allow for annealing in conventional batch annealing furnaces. The content of carbon in T-201L stainless steel was kept at less than 0.030 weight percent and the steel was successfully annealed at temperatures within a range of about 1650.degree. F. to about 1700.degree. F. The carbon content of T-304L stainless steel was kept at less than 0.015 weight percent and the steel was successfully annealed at temperatures within a range of about 1550.degree. F. to about 1700.degree. F. For light gauge strip, the winding tension of the coiled stainless steel was reduced prior to the batch annealing process. In particular, winding tensions of less than about 30,000 psi were beneficial, with good results being found when the winding tension was held within the range of about 15,000 psi to about 3,000 psi.